An account of the Crustacea of Norway V8-1 Copepoda Monstrilloida and Notodelphyoida

AN ACCOUNT
OF THE

CRUSTACEA
OF

NOR WAY
WITH SHORT DESCRIPTIONS AND FIGURES OF ALL THE SPECIES
BY

G. O.

SARS

VOL.

VIII

COPEPODA
MONSTRILLOIDA & NOTODELPHYOIDA
PARTS

I

&

II

THAUMATOPSYLLID/t, MONSTRILLID/ E,
NOTODELPHYIDfE (part)
C

WITH

16

AUTOTYPIC PLATES

BERGEN
PUBLISHED BYTHE BERGEN MUSEUM
SOLD BY

ALB.

CAMMERMfeYERS FORLAG. CHRISTIANIA
1921


lltllll
\

M


INTRODUCTION.
the

In

of

groups

the

now

more

has not been

fully

the

recognised by earlier authors.
Giesbrecht, and

Copepoda proposed by

adopted by carcinologists, only the systematic rank of families
these

to

and the NotodeLphyoida,

Monstrilloida

the

viz.,

anomalous

propose to give an account of 2

I

recent classification of the

generally

alloted

is

Copepoda,

position of which

systematic
In

volume

present

and they are both, together with several other
comprised within the 2nd tribe of this suborder Podoplea,

groups,

heterogeneous families,

which the name Ampharthraiidrla is given.
have otherwise shown, that
the principles upon which Giesbrechts classification is founded do not at all
to

I

hold good
here

in

cable

to

every case, and this

in

It

question.

the

may

Monstrilloida;

Notodelphyoida,

be

is

that

but

regard to the

also proved in

this

name

the
is

by

no

Copepoda

Ampharthrandria

is

means

with

the

case

appli-

the

group comprising many forms with the anterior antennae

this

Moreover, the genus Thaiiniatopsyllus among the
conspicuously even in the principal character by which

quite alike in the 2 sexes.

Monstrilloida
2

the

the

viz.,

body.

differs

suborders

mutual

The many

both from

of,

Gynuioplea
relation

other

by Giesbrecht,

distinguished

between the anterior and posterior divisions

of

the

groups here treated
and
known
each other
from the other
Copepoda, have led me
they ought to be raised to the rank of distinct divisions,

be again subdivided into real families.

to

are

essential characters distinguishing the 2

to the conclusion, that

a

and Podoplea

known groups

of

Copepoda

is

of the

relation of these divisions to

somewhat obscure, though

tendency towards the Cyclopoid type

by an extreme degradation

The

is

unmistakable.

whole body and

its

On

in

some

instances

the other hand,

appendages, some forms

belonging to the Notodelphyoida acquire an appearance, strongly recalling that
the Lemceoida.
All the forms here in question are in some measure

of

parasitic
1

in

Crustacea.

habits.

But the

parasitisme

is

of

a

very different

kind

in

the


2

The Monstrilloida

divisions.

are,

according to the interesting observations

of Malaquin, in their juvenile state true endoparasites, living as simple, sac-like

bodies
in

in

fully

some

invertebrate

developed natatory appendages.

whole

are for
all

the blood-vessels of

animals (Annelids), whereas

the adult state they are freely living pelagic animals provided with power-

their

life

The Notodelphyoida, on

confined to their hosts (simple and

the other hand,

compound

Accidians),

stages of growth being mostly found together in the branchial cavity of these

hosts,

they do

Yet

Tunicata.

but

not seem,

as

a

rule,

more properly on the nourishing

to

feed

particles

introduced, together with the constantly renewed water,

by the breathing process.
but

parasites,

on the juices of their
and small organisms
in

the branchial cavity

Of course they cannot at all be regarded as true
as commensals or messmates.
Both divisions

more properly

here treated of are well represented in the Fauna of Norway, and as there

some confusion

in

regard to the

is

exact definition of the genera and species,

and moreover the descriptions and figures given by earlier authors in many

cases are very incomplete and partly erroneous,
think that a thorough revision of
I

these

2

interesting groups,

of interest.

accompanied by good

figures,

cannot

fail

to be


MONSTRILLOIDA.
Remarks.- The
this

the

most prominent

of

Copepoda,
and
antennae
posterior
group

the total

is

morphological character distinguishing
absence,

the

in

adnlt

state,

both

of

of

any traces of oral appendages, as also of a
functional alimentary canal.
Of course the fully developed animal is quite
in
to
feed
the
incapable
ordinary manner, but may only subsist on the
accumulated

matter

nourishing

within

the

body-cavity

parasitic existence, the adult stage being exclusively

The

to the

its

Dana, with

identical.

they

interesting

number

formerly were referred to a single genus, viz., Monstrilla
which the genus Thanmaleiis of Kreyer was considered to
all

recent

In

into 2 or 3

juvenile

propagation.

division Monstrilloida comprises as yet only a rather restricted

forms, which

that

devoted

during

times,

it

is

true,

a

subdivision

of the

all

events must

be comprised within the same family.

new genus (Thaumatopsyllus),

of
he-

genus Monstrilla

genera has been attempted, but these genera are so closely

at

of

allied,

Yet an

apparently referable to the Monstril-

been added by the present author, and this genus is so
very different from the other Monstrilloid genera, that it cannot by any means

loida,

has recently

be included

in

the

same family with them, but must be regarded

as the type

not only of a separate family, but even of a distinct section, for which

proposed

the

Monstrilloida

name Monstrilloida cyclopimorpha.
appears

at

present

cleft

into

cyclopimorpha and the M. gennina; but each
represented by a single family.

2

well

I

have

Of course the division
defined

sections,

of these sections

is

the

M.

as yet only


Section

1.

Monstrilloida cyclopimorpha
The type

Remarks.
the

present

author

of this section

another

in

place

is

the remarkable form

under

the

name

of

described by

Thaumatopsyllus

The reception of this form within the division Monstrilloida
paradoxns.
character:
appears to be warranted by the above-mentioned general morphological
the

absence of both the posterior antennae and of any oral appendages.

total

Otherwise

this

form

differs

considerably from the Monstrilloid type.

Fam. Thaumatopsyllidae.
As

Remarks.

may be

this

at

family

present

only comprises

a

single

genus,

it

sufficient to give the characters of that genus.

Gen. Thaumatopsyllus, G. O.
Generic Characters.

Body

of adult

Sars,

female cyclopoid

division being conspicuously dilated, the posterior slender

consolidated

with

below

short

to

a

the

1st

trunkal

and blunt

segment,

rostral

1913.
in

shape, the anterior

and attenuated. Head

and having the

prominence.

The

2

front

produced

succeeding trunk-

segments normally developed, the 2 posterior ones, however, abruptly much
narrower and firmly connected with the tail, to form with it the posterior

movable portion
segments,

the

last

of

the

body,

Tail

proper composed

extremely slender and

in

narrow, rod-like.

female of only 3

Caudal rami well


developed, with the normal number of

number

limited

well

of

and

of posterior antennae

defined

Anterior antennae

setae,

and

joints,

extended

composed

No

laterally.

appendages observable, nor of any

oral

of a

traces

distinct oral

Three pairs only of natatory legs present, the 2 posterior pairs of legs
being quite rudimentary and of similar structure. Two ovisacs present in female.
have attempted to give the most
Remarks. In the above diagnosis

tubule.

i

by which the present genus distinguishes itself from the

The mutual relation of the 2 chief divisions of
other known Monstrilloida.
essential

the

characters,

body

very peculiar, and does not agree either with that mentioned by

is

Giesbrecht as characteristic to his suborder Gymnoplea or with that characterising
the

the

Podoplea,

movable

quite a different place,

viz.,

between the 2 divisions occuring in
the junction between the penultimate and anti-

articulation
at

penultimate trunk-segments. This
this

is

indeed a quite unique character distinguishing

genus from any other form known

here

be

rod-like

named

me.

to

the presence of only 3 pairs

shape of the

last

caudal segment.

As anomalous characters may also
of natatory legs, and the narrow

The genus comprises

as yet only

a single species, to be described below.

Thaumatopsyllus paradoxus, G. O.

1.

(Pi.
I

haiima topsylltis paradoxiis, O. O.

Specific

Characters.

i.)

Sars, Arch. f. Mathcni. og Naturvidenskab.
No. 6, p. 5, w. plate.

Female.

Body

comparatively

somewhat depressed and oblong

anterior division

Sars.

slender,

oval in outline.

Bd. XXXIII.

with

the

Cephalic seg-

ment very large and
narrowly rounded.
The 2 succeding segments well developed, with the lateral parts closely contiPenultimate trunk-segment scarcely more than
guous and rounded behind.
slightly contracted anteriorly, frontal part

half as

broad as the preceding one;

last

segment

still

smaller.

Tail exceedingly

slender, almost attaining half the length of the body; genital segment slightly

2nd segment quite short and having the posterior
edge somewhat produced dorsally; 3rd segment more than twice as long a>
the other 2 combined, and extremely narrow, rod-like, with the slightly dilated
constricted in the middle;

and oblong
form, being about 4 times as long as they are broad, and

extremity transversely truncated.

quadrangular
a

little

apical

in

widening
setae

of

than the other

distally;

moderate
3.

seta
size

Caudal rami but

slightly diverging

of outer edge occuring about in the middle;
and densely ciliated, the outermost one shorter

Antennae not nearly attaining

the

length

of the cephalic


segment, and each composed of 9 joints clothed with
3rd

joint

much

equal-sized.

same

the

6 outermost joints

the

largest,

The 3

scattered simple setae;

comparatively short and

normally developed and of essential

pairs of natatory legs

and nearly of equal size.
The
last 2 pairs of legs very unlike the former, and reduced to simple small
3-articulate stems, with the middle joint very small, last rounded in shape and
both

with

structure,

rami

3-articulate

Ovisacs very large, rounded oval

provided with 2 unequal apical spines.
in

Body

the

in

form.

animal highly transparent and nearly colourless,
9

living

its

part being filled up with a number of clear oil-bubbles of unequal
and partly of a light orange colour.
Eye replaced by a comparatively

anterior
size,

transverse

large

of

patch

a

light

red

in

pigment,

which,

no

however,

trace

elements could be detected.

of refracting

female 1.65 mm..

of adult

Length

Male unknown.
The above-described form

Remarks.
the

other

known Copepoda, both

as regards

structure of the several appendages.

history

will

turn

Monslrillidce,

and

that

existence within the

Occurrence.

female sex,

be

out to

in

body

a

of

some

Trondhjem Fjord,

at

Selven.

other pelagic animals,

about 60 fathoms.

to

Christiania
All

from any of

outward appearance and the

its

am much
one

Three specimens only

ago,

easily recognisable

inclined to believe, that

that stated
this

of

my

remarkable form,

this

notice.

Fjord,

at

One

Drobak,

of

similar

parasitic

the

all

the

of

them was taken,
other

2

the

in

3 specimens were captured, together with

by the aid of a plankton-net lowered to a depth
living animal was seen moving through the water

The

jumping manner to that observed in most Cyclopoida.
however, by no means particularly agile in its movements.
a

for the

by Malaquin

form leads a true

its life-

invertebrate animals.

have as yet come under
the

years

I

similar

the juvenile state

in

many

is

It

of
in

was,


Section

2.

Monstrilloida genuine.
Remarks.
general

section

this

In

characters

of

which

are

comprised the typical Monstrilloida, the
with

coincide

those

given

below

for

the

sole

family as yet representing the section.

Fam.

Body more

General Characters.
anterior

division

posterior.

rather

its

segment

more than

rostral

any

only slightly

Head and

a very large

length

1st

Monstrillidae.
and elongated, with the
dilated and not sharply marked of from the
or less slender

trunkal segment completely coalesced, forming together

of a

more or

half the body,

its

less cylindrical shape,

a rule

occupying

anterior extremity obtusely truncated, without

prominence; ventral face of the segment
quite

and as

in

the greater extent of

smooth, exhibiting no traces of either posterior antennae or

appendages, being only provided in the median line with a small
tubular process, from which a short canal leads to the inner substance of the
oral

any

latter in female specimens retracted from the walls of the segment
most peculiar manner, so as to form a rather narrow band-like chord

body; the
in

a

passing through the axis of the segment.
of 4 well defined

Exposed

segments gradually diminishing

in

part of trunk
size behind.

composed
Tail poorly

developed, with the number of segments more or less reduced, and exhibiting
well

with

marked sexual
strong plumose

differences.
setae,

the

Caudal rami, as

number

of

which

a
is

rule, short,

somewhat

but provided

variable in the


8

different genera.

and 2

ventral
is

of

limited

different

some

number

present

legs

the
of

basal

part

massive,

any

and

number,

very

and

muscular

setae

powerfully

rami

both

number

of

plumose

up the greater part

filling

the

within

pointing

in

with

developed,

3-articulate.

Last

pair

male much reduced, or

in

setae;

frontal

of

part

of

the

fully

developed,

and extending

body-cavity

head; the ripe ova not included

the

in

ovisacs, but agglutinated to 2 slender juxtaposed spines or filaments

true

from the ventral face of the genital

issuing

unequal

Alimentary canal quite obliterated. Ovaria, when

wholly absent.

anteriorly

;

and

joint carrying a restricted

very

rather

them being much elongated and finely ciliated,
the terminal joint, exhibiting not seldom a peculiar
same antennae in male distinctly hinged. Natatory

usual

large

with

and composed

straight forwards,

female represented on each side by a single more or less lamellar

in

legs

the

in

clothed

Anterior antennae, unlikr

of

attached to

others,

dichotomous ramification

highly refracting lenses, one

.'$

dark pigment.

a

in

Copepoda, extended

of joints

some

directions,

present, exhibiting

imbedded

lateral,

generally the case in

\vhat
a

when

Eye,

male replaced

a

by

somewhat

thickish,

segment, these spines being

in

appendage, into which the

clavate

spermatophores are received before extrusion.

Of

Remarks.

this

from 2 widely remote

family

localities,

at

only 2 species were known, derived

first

Dana from

the one recorded by

the Sulu Sea

the other by Kr0yer from thn Norwegian coast as
2 species, though bearing very different names,
These
typicns.
are evidently nearly allied, and were also by most subsequent authors regarded
as

Monstrilla

viridis,

Thaiimaleiis

as

forms

of
of

parts

the
the

according

to

more

In

congeneric.

same

recent

remarkable

oceans,

and

some

more

it

times

a

considerable

have

type

appeared

been

recorded

desiderable

conspicuous

number

to

additional

from

different

these

group

found

diversities

of

species

between

them.

Thereby the first step to a subdivision of the genus Monstrilla was intimated.
Such a subdivision was indeed carried out in the year 1892 by Giesbrecht,

who

referred

chiefly

the

the

Monstrillidae

characterised

caudal

Monstrilla,

setae.

for the

at

that

time

known

by the segmentation of the

to

tail

2 nearly-allied genera,

by the number

and

of

For the one of these genera he retained the old name
other he applied the name Tlianmaleus proposed by Kr0yer,

am
arrangement has now generally been admitted by carcinologists.
am by no
also of opinion that these 2 genera should be supported
but

and

this

I

;

means prepared to consent with Giesbrecht
haumalens to the one of these genera. For

7

recorded by Kr0yer

is

in
it

his
is

application

I

of

the

name

quite certain, that the form

not referable to Giesbrecht's genus, differing as

it

does,


one

just in

from

of the 2 principal characters

Monsttilla,

in

viz.,

the

description given by Kr0yer in

number

by whieli that genus

is

distinguished

Both according to the
"Naturhistorisk Tidsskrift" and to the figures in the
of caudal setae.

Gaimards voyage, the caudal rami in Kreyers species are each provided
with 5 well-developed setae, as in most species of the genus Monstrilla, whereas
Atlas to

in

Giesbrecht's genus the

number

ramus

last

occuring on

found

each

advisable

to

(at

of. setae
in

In

female).

confined to the species recorded by that author.

name

generic

to

as

Cymbasoma, proposed
a

genus Hcemocera

early

of

Malaquin

the

establish

thus
of

at

name

Cymbasoma,

all

his

to

C.

I.

must be

genus,

Thompson

of

I

that genus.

have found

it

viz.,

for

The
In

advisable

anomalous species

include the

The family

which are represented

Monstrillidae

the fauna

in

Norway.

Though

I

have not myself as yet had any opportunity

peculiar life-history of the Monstrillida?,

made

interesting investigations

here

may
the
in

to

of Monstrilla dubia.

present comprises 3 genera,

it

we have another

synonymous with

as

another genus, Moiistrillopsis,

described by Scott under the

by

should be

it

Kreyer,

Fortunately

1888

year

regard

I

of

if

referable to Giesbrecht's genus.

is

addition to the 2 genera Monstrilla and
to

any case,

Giesbrecht

by

given
as

which evidently

(rigidum),

species

that

replace

reduced, only 3 such setae

genus Thaunialens

the

support

much

is

be given.
as

eggs

front with

the

think

in this respect

According

small Nauplii,

I

that

a short

by the French

to

resume"

naturalist

to that distinguished author,

the

some

to

cells

all

completely

bodies

merely

surrounded by

horn-like processes

their

consisting

a thin

grow

an

of

1

)

live

of

their position they

The Nauplii

By

this

to

process

simple

assemblage of indifferent embryonic
the one end of these bodies 2 soft

From

cuticle.

out, gradually increasing in length,

appendages the absorbtion
to

young

appendages, and become converted

and

at last

assuming
supposed that through these
the blood-serum of the host is performed, and

the form of slender thread-like appendages.

according

Malaquin

polychaete Annelid and penetrate through the

body-wall of the same, then entering the vascular system.

ovoid

the

without mouth or alimentary canal, but provided

behind them on each side with a hook-like appendage (mandibles).

lose

of

the

usual 2 pairs of limbs (anterior and posterior antennae) and

soon attach themselves

they

study

may answer

It

to

is

the posterior antenna?.

During

the rapid growth of these endo-parasitic larvae a remarkable differentiation take

place in their interior, resulting in the formation of the characteristic and rather

';.

2

See:

Crustacea.

Arch. Zool. Exp.

(3),

Vol.

9,

1901.


10

complicated body of
Monstrillid

is

a

Monstrillid.

true

the last larval stage the enclosed

In

very distinctly traced through the thin outer cuticle of the larva,

up nearly the whole inner cavity, and exhibiting all the
dages, as also d stinct traces of the generative organs, at
filling

At this time the larva

ones.
host,

and

this

several

Its

appendages
moult,

single

commence

its

it

movements

is

thin

its

of small

outer cuticle soon

thus allowed to emerge, unfolding

its

lather slow, but very soon,

by

first

moving

development,

quickly

about, to

free pelagic existence

Syn:

2.

Monstrilla, Dana,

Thaumaleus, Kroyer

?

Generic Characters.

Body

and more or

length

1848.

(not Giesbrccht).

and elongated, especially
most cases occupying rather more than

as a rule very slender

female, with the cephalic segment in
its

out of the body of the

surrounded with several rows

are at

full

its

aquires

Gen.

half

way

its

escape of the larva

the

After

is

and the enclosed Monstrilltd

burst,

in

which

extremity,

hooklike spinules.

a

ready to force

appen-

the female

least

apparently accomplished by a burrowing action of the hind

is

produced

acutely

is

definitive

shape; exposed part of trunk

in

less cylindrical

gradually narrowed behind, with the lateral parts of the segments rounded
Tail

female of

in

male

in

off.

of 4 well defined segments, the last

3,
composed
4
Caudal rami sublamellar,
one rather small and obtusely truncated behind.
each provided in female with 5 or 6 setae, one of which is generally shorter

than the others and attached more dorsally; those

one

as in female, but lacking
fectly

developed.

of the head.

comparatively

tubule

Antennae more or

fectly defined in

setas;

Oral

of the setae.

female.

short,

bulh

generally

laterally,

clothed

Last pair of legs

(in

same appearance

from

the

frontal

part

imper-

inside

and
the

in

at

the end with long

inner and
1st joint,

only

plumose

provided with

the other to the end

female sublamellar and somewhat extended

expanded, extremity slightly exserted and
some cases only 2) plumose setae; those in male much

more

inner edge

provided with 3

remote

of

of the species imper-

Natatory legs with the basal part very massiv, rami

2 small spines outside, the one attached to the
of the last joint.

male

most

less elongated, with the joints generally

somewhat longer than

outer ramus

Eye
far

in

in

or

less

and tipped with one or two slender setae.
Remarks. The present genus was established as early as in the year
1848 by Dana, and may be legarded as the type not only of the family Mon-

reduced

strillidae,

in

size, knob-like,

but

also

of the

whole division here treated

of.

It

is

chiefly distin-


11

guished from the

other 2 genera comprised within the present
family by the
complete segmentation of the tail and the increased number of caudal

more

Another character by which the species of

setae.

recognised,

is

from the frontal part of the head, whereas

genus may be readily
more or less far remote

this

the position of the oral tubule, wich

is

other 2 genera

in the

it

generally

occurs in close approximation to that part.

Seven Norwegian species referable to this genus will be described in the
sequel, one of them being, however, somewath doubtful and only observed in
the male sex.

Monstrilla longicornis, Thompson.
(Pi. II & ill).

2.

Monstrilla longicornis,

I.

C.

Thompson, Trans.
figs.

integuments,

which

2,

Liverpool, Vol IV,

Biol. Soc.

p.

119, PI. IV,

4 (cf).

Mcnstrilla intermedia, Aurivillius.

Syn:

Female.

Specific Characters.

1,

exhibit

Body moderately

everywhere

a

finely

slender, with rather coarse

granular or dotted

surface.

Cephalic segment occupying about half the length of the body, and almost of
equal width throughout, though, seen dorsally, exhibiting somewhat behind the

middle

a slight but easily observable dilatation,

Tail about equalling half the length of the

frontal part bluntly truncated.

exposed part

comparatively large, being fully as long as the

segment
tail, and oblong quadrangular
in

the

the

tail.

and

slightly

divergent,

nearly equal size, the

scarcely exceeding in

posed

each

provided

with 5 strong plumose

somewhat

a

setae

of

well-marked ledge of the

obliquelly rounded apex.

Eye imper-

developed, without any trace of refracting elements, and only replaced
diffuse yellowish

a

of the

shape, with a well marked transverse suture

outermost one attached to

outer edge, the others to the

by

remaining part

middle of the dorsal face; ovigerous spines about twice the length of
Caudal rami about equalling in length the last 2 segments combined,

only

fectly

in

of the trunk; genital

of

5

joints,

of

pigment.

Antennae rather slender and elongated, though

length the cephalic segment, and each apparently com-

which, however, only the

1st

is

distinctly defined, the

others being confluent and only indicated by slight constrictions of the antenna;

most of the

setae

attached

around the middle of the fusiform terminal

joint

Oral tubule well marked and occurring somewhat behind the
reachly ramified.
middle of the cephalic segment. Natatory legs all of the very same structure and
also of about equal size;
1st,

2nd basal segment not very sharply defined from the

and armed inside with 2 small juxtaposed denticles; terminal

joint of outer

12

ramus

marked

the outer edge divided into 4 very distinctly

broad

rather

legs

and having

rather produced, being fully twice as long as the middle one,

having the outer part abruptly narrowed

but

the base,

at

Last pair of

crenulations.

and provided at the obtusely rounded extremity with 3 ciliated setae, the innermost of which is much smaller than the other 2; inner expansion almost rectangular and carrying

a

single, but well

Male considerably

than

smaller

segment.
4

below

club-like

to a

armed

rami, each

of

segments

at

than

in

1st,

legs

produced

one

Antennas more strongly

of the apical setae absent.

same

structure as

last

2 joints. Natatory

prominence tipped by 2

cases only

slender

1)

common

setae.

both sexes of a yellowish grey colour, and on the whole

in

Body

some

(in

much

Last pair of legs, however,

female.

i

size, forming 2 small knob-like prominences issuing from a

in

each

base,

as usual,

of

female and having the joints more distinctly defined, being more-

in

exactly

reduced

cephalic

appendage terminating in 2 short diverging
the end with a short spine. Caudal rami of a similar shape

over conspicuously hinged, the hinge occurring between the
of

of the

and

female, and composed

length, the

equal

shorter

copulative

to that in female, but with

built

nearly

somewhat

of

very similar shape

a

comparatively more slender than

defined

well

and

female

stouter form of the body, but exhibiting
Tail

seta.

developed

transparent than in most other species.
Length of adult female 3.50 mm., of male 2.30

less

mm.

Remarks. This species was established in the year 1890 by J. C. Thompson, and was only based on a solitary male specimen taken by him off the
Puffin Islands.

Subsequently, however, Th. Scott recorded this form from

other localities, and has given

(1904)
that

good

and

descriptions

Giesbrecht's species,

but

him;

this

present species

is

certainly

may

M.

the report of the Fishery

in

figures

longiremis,

not

the

both

of

case,

is

as will be

be easily distinguished from

what robust body and the rather coarse and

Two

other

legs,

may

ment

of

characters,

also

here

both

derived

be named,

viz.,

from

its

shown

that

Scotland

of

opinion

observed

further on.

by

The

nearest allies by the some-

structure

of

the presence inside the

the

natatory

2nd basal seg-

2 well defined denticles, and the very conspicuous crenulation of the

constant and found quite alike

in

both sexes.

under the name of M. intermedia
Occurrence.

both

with

is

many

for

distinctly granular integuments.

the

outer edge on the terminal joint of the outer ramus.

lius

He

sexes.

identical

Board

I

have met with

on the south and west coast

is

this

of

These characters are pretty

The form recorded by

Aurivil-

identical with the present species.

form occasionally

Norway, among

in

several

places,

other pelagic animals


taken by the aid of the tow-net near the surface of the sea.

animal

the

of

the

body

occur

in

is

are

very
in

kept

nearly

British

3.

Monstrilla

rapid,

more

a

in

The movements

abrupt bounds, whereby
Male specimens seem to

or less erect position.

same number

Distribution.

and are performed

as the females.

Isles

(Thompson,

Skagerak

Scott),

(Aurivillius).

Monstrilla longiremis, Giesbrecht.
(PI. IV & V)

longiretms^Giesbrccht, Pehigisclie Copepoden des Golfes von Ncapel,
4
the preceding species, with

14,

p. 589,

PI.

than

in

22, 37, 41.

Body considerably more

Female.

Characters.

Specific

10,

figs.

thinner and scarcely

at

all

slender

granular

integuments.

occupying rather more than half the length of the body,
narrowed in its anterior part, with no distinct dilatation in the

Cephalic segment

and

slightly

middle.

and

Tail

its

agreeing with

segmentation,

Caudal

elongate.

that in

but

rami

M.
the

having

comparatively

remarkably divergent; number

of

longicornis, as regards

ovigerous

narrower

marginal

than

setce,

that

in

M.

in

relativ size

considerably

spines

as

its

species

all

having

length

a

in

denticle

any. crenulations
of

pair

attached

inside

M.
the

mulated

to

Male
a

much

nearly

in

the

preceding species,

-Oral tubule rather small, and

Natatory legs resemb-

longicornis, but differing in the presence of only

2nd basal segment, and

on the outer edge

legs comparatively

to

1st,

as

and,

confluent.

the middle of the cephalic segment.

minent and evenly rounded

Ova

segment,

cephalic

structure those in

single

Last

the

the joints, except the

occurring about
ling in

Eye

Antennae exceedingly slender and elongated, considerably ex-

inconspicuous.
in

and

longicornis, 5 on

each ramus, the innermost but one conspicuously shorter than the others.

ceeding

more

outer ramus.

of the terminal joint of the

narrower, with

number

off;

the total absence of

in

of

the inner expansion less pro-

marginal

the genital spines very numerous,

form an oblong oval mass extending

far

M.

longicornis.

some

cases accu-

setae as in

and

in

beyond the

limits of the body.

of rather small

similar

perfectly

size, as compared with the female, but exhibiting
and narrow form of the body.
Cephalic segment
in
in length the
and
somewhat
cylindrical
exceeding
shape

slender

remaining part of the body.

Tail,

4-articulate, with

the copulative

rami agreeing

shape with those

in

as in the

appendage
in

male of M. longicornis,

of a very similar structure.

female and spread out

in

the

distinctly

Caudal

same remark-

manner, each of them, however, only provided with 4 setae. Antennae
much more slender than in the male of M. longicornis, with the 2nd joint of

able


unusual

otherwise

length,
as

exactly

with

only tipped

Body

much

a

in

similar

Last pair of legs, however,

manner.

Natatory

legs

very small, knob-like, each

slender seta.

a single

both sexes rather pellucid with only a very slight yellow tinge, and

in

some

in

provided

female.

in

built

places with a few small pigmentary patches of a darker colour.

Length of adult female generally about 3 mm., though

in

mm.; that of male scarcely attaining 2 mm.
Remarks. The above-described form is unquestionally

some

instances

reaching 3.70

same

the

as that

by Giesbrecht from the Mediterranean, the identity of both being

recorded

once seen by

a

work.

true

is

It

of these 2

the

that

present

form

in

given with those

in

several

shows

respects

Giesbrecht's
a

near

M. longicornis; but I think that the above given descriptions
will prove them to be in reality specifically distinct.

to

relationship

of the figures here

comparison

at

forms

Occurrence.

Several

specimens

of

form have been taken by

this

me

at

and

in

different places on the Norwegian coast, from the
and
Christiania Fjord
northwards to Kval0. Only a single male has, however,
as yet come under my notice, all the other specimens were of the female sex.

different

times

Mediterranean (Giesbrecht).

Distribution.

Monstrilla clavata, G. O. Sars,

4.

considerably dilated

length

dorsal

of

face

exposed part

in

its

sp.

rather

Body

and viewed

anterior part

and

stout

clumsy,

laterally, of a

being

pronouncedly

Cephalic segment very large, occupying rather more than half

clavate shape.

the

Female.

Characters.

Specific

n.

VI)

(PI.

the

body, and

having

remarkably vaulted
the

of

trunk,

the 2 preceding species;

in

its

greatest

front.

Tail

width about

the middle,

in

about half the length of the

and on the whole resembling

in

structure that in

ovigerous spines rather produced, being

fully 3

times

Caudal rami exceeding somewhat in length the last 2

long
segments combined, and only slightly divergent, each, as in the 2 preceding
as

as the

tail.

one being, however, considerEye inconspicuous. Antennse not nearly attaining

species, provided with 5 setae, the innermost but

ably shorter than the others.

the length of the cephalic segment, otherwise built in
as in

the 2

preceding species.

somewhat behind

M.

the

longiremis, armed

Oral

tubule

much

rather prominent

middle of the cephalic segment.
2nd basal segment with

inside the

denticle, terminal joint of outer

ramus with

a

same manner

the

and occurring

Natatory
a single

legs,

as in

well-marked

slight indication of a crenulation


outer

the

of

Last pair of

edge.

very similar

legs

in

shape

to those in

M.

longicornis, the inner expansion being rather prominent.

animal whitish pellucid, and ornamented with irregular

in the living

Body

brown

patches of a light reddish

or chestnut-coloured pigment.

mm.

of adult female 4.50

Length

Male unknown.
Remarks.
I

therefore at

examination
from

ally

is

the largest of the species observed by me, and

be the M. grandis

to

it

have, however, found

I

shape

being

though

species,

in

it

easily

much more

a closer

respects very essenti-

nearly related to the 2

them

from

distinguishable

On

by

the

rather

A

solitary

female specimen

of

this

form was taken,

many

Hval0r, outside the Christiania Fjord.

at

Monstrilla leucopis, G. O. Sars,

5.

(PI.

Female.

Characters.

Specific

somewhat

resembling

some

to differ in

reality

of Giesbrecht.

of the body.

Occurrence.
years ago,

much

believed

that species,

preceding
different

-This
first

in

sp.

VII)

Body exceedingly

that

shape

n.

of

M.

slender and elongated,

segment

Cephalic

longiremis.

considerably exceeding half the length of the body, and of a narrow cylindrical
form.

Tail

comparatively short, scarcely

posed

part

of

the

without any trace

trunk;
of

Caudal rami rather

and only

dorsal

a

segment

suture;

rather

dilated

at

the

base,

ovigerous spines of moderate

large, exceeding in length the last 2

divergent,

slightly

genital

attaining half the length of the ex-

and

length.

segments combined,

inner edge perfectly straight,

outer considerably

protuberant in front of the middle; each ramus provided with 5

setae,

3 of

which issue from the narrowly rounded apex, the other 2 from the outer edge,
the latter of very unequal size, the proximal one being normally developed,
whereas the

distal

one

is

greatly reduced, and only slightly exceeds in length

Eye inconspicuous, and replaced by an opaque
whitish substance apparently answering to the ocular pigment. Antenna rather
slender, though not nearly attaining the length of the cephalic segment, and
the

corresponding ramus.

having their 5 joints

none
small,

of the

setae

more

distinctly

defined than

in

the

attached to the terminal joint ramified.

and occurring somewhat

in

front of the

preceding species,
Oral tubule rather

middle of the cephalic segment.

Natatory legs without any denticle inside the 2nd basal segment, outer ramus
rather

produced

and having the outer edge

of

the

terminal

joint

perfectly


_
smooth.

Last

with 2 apical

of

pair

legs

16

narrowed

gradually

and only provided

distally,

inner edge scarcely expanded.

setae,

Male much smaller than female, but exhibiting
form of the body.

as usual,

Tail,

very

similar slender

of 4 well defined segments, the

composed

and

a

produced below to a rather large and
prominent copulative appendage of an oblong oval form and armed on each
side with a straight rod-like spine.
Caudal rami of the very same shape as
1st

in

which

of

the

the

is

largest,

is

and having the outermost but one of the

female,

reduced

setae

in

a

similar manner, differing, however, as in the males of the preceding species, in

the absence of one of the apical

manner.

Last pair

each tipped with

Body

of

a

slender seta.

female) highly transparent and ornamented in

(in

mm.;

reduced to 2 very small knob-like prominences,

legs

single

pigmentary patches of
to 3.30

Anterior antennae hinged in the usual

setae.

that of

Remarks.

I

reddish colour.

a light

some doubt,

in

if

mm.

not the above-described form

should be the same as that recorded by Scott under the

Lubbock.

in

Indeed,

the

structure

the last

of

agree pretty

to

judge

On

well.

from

the

essential difference

the

given

figure
is

other hand,

by

Scott,

is

name

of

and the peculiar
both these forms seem

setae,

the general shape of the body,

rather

unlike,

and another very

found as regards the number of the caudal

setae,

both according to the description and the figure given by Scott,

be 6 on

name
by

it

ramus

in

the form observed by him.

In

is

which,

stated to

any case the specific

anglica cannot be applied either to the present form, or to that observed

Scott,

them.

each

M. anglica

pair of legs

reduction of the outermost but one of the caudal
to

places with

of adult female reaching

Length

male scarcely exceeding 1.60

have been

some

I

as

it

seems evident

have retained

long ago

in

my

Occurrence.

that

Lubbock's species

for the species

is

different

here treated of the

from both of

name assigned

to

notes.

Some

male, were collected,

6.

few specimens of

many

years ago,

at

this

form,

among them

Kval0 on the Nordland

a

single

coast.

Monstrilla gracilicauda, Giesbrecht.
(PI.

Monstrilla gracilicauda, Giesbrecht.

PI.

Specific Characters.

VIII)

Pelagische

46, figs. 9,

Female.

16,

Copepoden des Golfes von Nenpel,
18,

Body moderately

division slightly dilated in the middle.

p.

587,

29, 32, 43.

slender, with the anterior

Cephalic segment about occupying half

17

the length of the body, and, viewed dorsally, exhibiting a very slight dilatation
in

front of the middle, frontal

of

the

antennae.

Tail

edge somewhat produced between the insertion

exceeding half the length

of the

of the

exposed part

trunk; genital segment rather large, being considerably longer than the remaining
of the

part

transverse

and gradually narrowed behind, dorsal

tail,

suture

the

in

face with a very slight

Caudal

ovigerous spines unusually short.

middle;

rami comparatively small and somewhat divergent, each provided with 6

one

of

which,

however,

easily observable
lateral

somewhat

very short and attached
of a

dorsally.

somewhat incomplete

animal, though
and rather remote from each

lenses small

narrow

is

in the living

setae,

Eye

structure,

other, being connected by

dark pigment, ventral lens apparently imperfectly developed.
Antennae rather shorter than in the species described in the preceding pages,
a

stripe of

not even attaining half the length of the cephalic segment, and only
of

4 joints,

the

of

last

somewhat fusiform

in

occurring unusually

far

segment.

shape,
in

considerably

none

with

front,

longer

clavate

in

immediately

outline,

the

inside

the

of

the

ramified.

setae

about the end of the

at

denticle

any
than

well developed, with the outer

somewhat

composed

about as long as the other 3 combined and

is

Natatory legs without

outer ramus
joint

which

the

inner

and

apical

forming

setae

3

in

of the cephalic

2nd basal segment,
having the

edge perfectly smooth.

inner edge

extremity,

first */3

inside the

Oral tubule

a

terminal

Last pair of legs

rounded expansion

number and

of

nearly

size.

equal

Body

in

the living animal rather transparent and in

some

places tinged

with a light yellow pigment.

Length

of adult

female reaching to 3.55

mm.

Male unknown.
Remarks.
in

the

The present

species

is

easily distinguished from those described

preceding pages by the comparatively shorter antennae, the position of

and the shape of the last pair of legs.
The tail, moreover,

appears more elongate and the genital segment of larger size than in those species.

the oral tubule,

Occurrence.
Some few specimens of this form, all of the female sex,
were collected, many years ago, in 2 different places on the Nordland coast,
viz., Valdersund and Kval0.
Distribution.

Crustacea.

Mediterranean (Giesbrecht) Scottish coast

(Scott).


18

Monstrilla helgolandica, Glaus.

7.

(PI.

somewhat

dilated in

the length

of

with

shape,

its

anterior part.

greatest

the

width

a

12, fig.

and

short

9.

stout,

and

Cephalic segment about occupying half

somewhat fusiform

dorsally, exhibiting a

little

in

Tail of a similar

length.

165, PI.

p.

Body comparatively

body and, viewed

the

the

half

attaining

Female.

Characters.

Specific

IX)

Die freilebenden Copepoden,

Monstrilla helgolandica, Glaus.

front

shape

middle and almost

the

of

to that in

M. gracilicauda,

the genital segment being rather large and gradually narrowed behind; ovigerous
of

spines

oblong

in

shape, each provided with 6 setae of

somewhat

of them, attached

outer side

Caudal rami considerably divergent, and narrow

moderate length.

somewhat

somewhat unequal

dorsally, being very small, that next to

shorter

than the 4 remaining ones,

from the outermost rounded part of the ramus.
all

having

Eye

all

easily observable,

and

in

composed

of

the middle of the

Natatory legs without any denticle inside the 2nd basal

cephalic segment.

segment, outer

on the

Antennae scarcely attaining half the

3 lenses distinctly developed.

Oral tubule well marked, and occurring about

joints.

it

one

the setae issuing

length of the cephalic segment, and, as in M. gracilicauda, only
4

length,

ramus

joint of smaller size.

elongate than

less

in

the other species, with the terminal

Last pair of legs rather unlike those in the other

each forming a narrow cylindrical stem, angularly bent
and tipped with 2 subequal setae.

species,

Body very transparent

in

its

in

known

the middle

anterior part, but behind tinged with a dark

brownish pigment.
Length, of adult female scarcely exceeding 1.40

mm.

Male unknown.
Remarks.

This

recognised

easily

is

a

very

small-sized

species,

and

by the unusual short and stout form

may moreover be
of

the body, as also

the caudal rami and that of the last pair of legs.
The
by
form recorded by Bourne as M. helgolandica is quite certainly not that species,
but more properly referable to M. longiremis Giesbrecht.
the

structure

Occurrence.

under

my

notice.

of

Two

female specimens only of

this

They were taken, many years ago,

form have as yet come
at

coast of Norway.
Distribution.

Helgoland (Claus), Skagerak (Timm).

Christiansund,

west

19

Monstrilla serricornis, G. O. Sars,

8.

(PI.

X, fig.

n.

sp.

1).

Male.
Specific Characters.
Body comparatively short and stout, and,
seen laterally exhibiting a somewhat clavate shape.
Cephalic segment shorter
than usual, only slightly exceeding in length the exposed part of the trunk
and, seen dorsally, nearly of equal

Tail

tubule.

oral

the

which

of

1st

at

provided

width throughout,

ventral face forming

its

prominent gibbous convexity, but without any distinctly marked
rather narrow, and composed of 4 well defined segments,

anteriorly a rather

produced below to
the end on each side with
is

a sub-clavate copulative

a

short

auriculiform

appendage
Caudal

lobe.

comparatively small and somewhat divergent, each having the form

rami

of

rounded oval lamella edged with 5 subequal setae. Eye inconspicuous. Antennae about equalling in length 2 /3 of the cephalic segment, and rather strongly
a

being composed of 5 well defined

built,

articulated

to

joints, the last of

which

as usual,

is,

preceding one, and somewhat knife-shaped,

the

very

movably

with

the inner sharpened edge divived at the extremity into 5 small recurved

denticles.

Natatory legs of the usual structure.

Colour not yet ascertained.

of the

Length

5th pair of legs wholly absent.

body 1.75 mm.

Female unknown
Remarks.
markable form

only provisionally that

is

It

observed,
liar

refer

genus Monstrilla, from which

to the

to differ rather conspicuously.
its

I

As,

it

may

some

in

respects

re-

seems

however, only the one sex as yet has been

true relationship cannot at present be fully

armature of the antennae

above-described

the

made

suffice to distinguish at

out.

once

this

The pecuform from

any of the hitherto known Monstrillidae.
Occurrence.

under

my

Two

specimens only of the present form have as yet come

notice, both of the male sex and exactly agreeing with each other.

The one was taken
on the Nordland

at

Bukken, outside the Stavanger Fjord, the other

at

Kval0,

coast.

Gen.

Cymbasoma, Thompson,

3.

Syn

:

1888.

T/iatnaleus, Giesbrecht (not Krdyer).

Hcemocera, Malaquin.

Generic Characters.
strilla.

Tail

General form

of the

however having the number

only 2 segments being present

in

body resembling

that in

Mon-

segments reduced in both sexes,
female and 3 in male. Caudal rami comof


20
short and

paratively

vided

or less pronouncedly club-shaped, each

female with only 3 distinctly developed

in

trary to

more

what

is

one additional

Eye

occurring

generally

head.

part

the

legs

in

female

far

in

in

built

in

more elongate, and
2 joints.

last

the

usual

manner.

provided inside with

but

short,

comparatively

in

Oral

close approximation to the frontal

front,

Natatory legs

con-

male,

generally increased by

male much

in

joints,

in

Antennae rather short

well-marked hinge between the

distinctly 5-articulate, with a

of

is

as a rule well developed.

female and only composed of 4

tubule

number

the case in Monstrilla, their

seta.

whereas

setae,

ramus pro-

Last
a

of

pair

well defined

lobe; in male wholly absent.

Remarks.- Tins genus was proposed
son,

to

include

a

peculiar

single female specimen

Copepod

was found.

(C. rigidum),

As,

on

a closer

specimens taken by the same author partly
British

referred

coast,
to

the

the

Cymbasoma was

near

relationship

genus Monstrilla of

the year 1888 by

in

of

in

this

of

which

in

C.

Thomp-

first

only

a

examination of several other

the Mediterranean, partly on the

form to the species

Dana was recognised,

subsequently withdrawn

J.

at

at that

the generic

favour of that of Monstrilla.

time

name
By

the

subdivision of the latter genus into 2 nearly-allied genera carried out by Giesbrecht,
it

was, however, of course required to decide to which of these 2 genera the species

of

Thompson should

is

quite certainly a true

be referred, and

member

of the

in

this

genus

to

regard no doubt can

arise.

which Giesbrecht had applied the

name Thaumaleus. Since, however, as stated above, the application
name to the present genus is quite inadmissibel,
have felt justified to

of this

restore

I

the generic

name proposed by Thompson.

The genus here treated
reduced number of segments
of

caudal

absence

in

chiefly distinguished from Monstrilla

of

is

in

the

tail,

and, by the likewise reduced

by the

number

Moreover the position of the oral tubule and the total
the male of the 5th pair of legs may be named as characters di-

setae.

stinguishing the present genus.
in

It

the succeeding pages.

Three well defined species with be described

21

Cymbasoma

9.

X,

(PI.

C.

J.

rigida,

rigidum, Thompson.
2,

fig.

PI.

XI).

Linn- Soc. Jouru. /.oo!., Vol.,

Thompson,

XIII,

figs.

XX,

p.

l.'il,

PI.

1-4.

Monstrilla rigida, Bourne
Thainnalens rigidus, Scott.
1

Syn

.

:

Thanrnalens Clapnredi. Giesbrecht.
Tfuuinialens gertnanicus, Tim in.

Htrmocera Dance, Malaquin.

.

extended

ment

in

somewhat

manner

a

to give

a

it

Body moderately slender, and generally
somewhat rigid appearance. Cephalic seg-

long as the remaining part of the body and, viewed dorsally,

as

fully

Female.

Characters.

Specific

dilated in the middle, ventral face evenly

convex throughout.

Tail

scarcely

exceeding half the length of the exposed part of the trunk; genital

segment

of

3

moderate

times as long as

and evenly narrowed behind, ovigerous spines nearly
the tail; distal segment somewhat flattened and gradually
size

widening behind, exhibiting

in

any difining

not

much

front

the

of

on each

middle,

Caudal rami only

suture.

divergent, with the

which

of

cular bristle

ventral

edge somewhat

inner

face.

joint

first

attaining

somewhat

shorter

1

U

slightly

pair

well developed, with

Eye

scarcely

Oral

ramified.
of

the

tubule

/a

than
rather

of legs with

the

3 apical

3 lenses distinct.

all

the length

of

the

its

inner,
setae,

3

other

the outer-

to the

Antennas rather

the cephalic segment, terminal

of

combined, with none

and occurring

small,

cephalic segment.

longer than

the other

setae,

moreover generally found attached near the inner corner

is

and

concaved, the outer gib-

attached to a rather prominent ledge; a very small appendi-

is

l

short,

a slight

slightly longer than they are broad,

bously produced, each ramus provided with 3 strong subequal

most

side,

attempt to a subdivision, the notch not being, however, continued

an

as

notch,

in

at

about the end of the

Natatory

legs with the outher

terminal

joint

the innermost of

of the setae

ramus only

much produced. Last

which is much smaller than
not

inner edge produced to a narrow linguiform lobe curving outwards

2,

most cases extending as far as the
latter.
Ova attached to the genital filaments very numerous and in some
cases accumulated to form an elongate almost cylindrical mass extending far
along the terminal part of the

beyond the
Male,

form
Tail

of

and

in

limits of the body.

as usual, smaller than female

the

rather

leg,

body,

with

the

and

of

cephalic segment

narrow and composed

of

a

shorter

somewhat

3 segments, the

last

and more robust
clavate

in

outline.

exhibiting on each


22

side

notch

quite similar

a

to

that observed in female; copulative

divided at the end into 2 comparatively large diverging lobes of a

sausage-shaped form.

Caudal rami more pronouncedly clavate than

each provided with 4 slender subequal
thickened

distinctly

appendicular
in

bristle

extremity,

found

in

preceding one, and terminating
of

same

exactly

slightest trace

Body

to

is

structure

last joint

female,

in

a

as

in

very movably articulated to the

slender, slightly curved spine.

female.

Of

Natatory

a 5th pair of legs not the

be detected.

of female, as usual, very transparent in

its

anterior part, but other-

wise exhibiting a light yellowish-grey colour, and tinged
a darker

in

attached to the obtusely truncated and

one of them apparently answering to the small
Antennae much more elongate than
the female.

female and distinctly 5-articulate,

legs

setae

appendage
somewhat

in

some

places with

brownish pigment.

Length of adult female reaching
That

Remarks.

to 2.50

form

the

is

mm.,

of

identical

male
with

to

1.75

mm.

recorded

that

present
by
the
-name
of
under
and
Thompson
Cymbasoma rigidnm
subsequently
more fully described by Scott as Thaiimaleus rigidus, appears to me to be
I.

C.

beyond any doubt, and

1

am

also of opinion, that several other forms, described

under different names, should be referred to that species. Indeed,

have been
unable to find any reliable character to distinguish the several forms enumerated
I

above as synonymes, and

I

am

thus led to the conclusion, that they

be combined into the very same species, for which of course the

ought

to

Most

come

a closer

name

earliest

have been taken by me
both on the south and west coast

Several specimens of this form

times and

Norway.
also

should

be retained.

Occurrence.
different

all

in

of the

different

places,

specimens collected were of the female sex; but

I

at

of

have

across a few male specimens, one of which has been subjected to

examination and

Distribution.

(Giesbrecht),

is

Atlantic

coast of

figured on PI. X.

Ocean

off

Teneriffe

Normandie (Claparede),

Eastern part of North Sea (Timm).

(Thompson).

British Isles

Mediterranean

(Thompson,

Scott),


23

Cymbasoma Thompsoni,

10.

(Giesbrecht).

XII)

(PI.

Thaiimaleiis Thompsoni, Giesbrecht, Pelagische Copepoden
PI.

46, figs.

des

Golfes

von

Neapel,

p.

584,

27, 31, 36, 40.

7,

Syn. Monstrilla Dana, Moebius (non Claparede)

Body comparatively more

Female.

Specific Characters.

slender than in

preceding species, with the cephalic segment narrower and considerably

the

exceeding

in

length the remaining part.

the last 2 trunkal segments combined;
dorsally almost circular

Tail very short, scarcely longer than

genital

segment unusually tumid, seen

outline, ventral face strongly protuberant, ovigerous

in

spines of moderate length; distal segment without any traces of lateral notches.

Caudal rami rather small, each provided with 3 subequal
bristle

YS

Eye apparently

present.

of the

well

length

part

of

longer

than

the

head.

the

Natatory

with

legs

and the terminal

inner,

of a structure very similar to

Oral tubule somewhat more approximate to the

that in the preceding species.
frontal

Antennae scarcely attaining

developed.

cephalic segment, and

the

of

no appedicular

setae;

ramus considerably

outer

the

more produced than

joint

in

the

Last pair of legs resembling in structure those in C. rigidum,

preceding species.

though having the innermost

of the

rather smaller

setse

apical

and the lobe

of the inner

edge less prominent.
Male comparatively more slender than that of the preceding species,
and having the cephalic segment shorter and less pronouncedly clavate in
shape.

Tail

female,

does not

very same

last

exhibit

3 well

defined segments, the

any traces

of

lateral

very

one very mobile

armed with
Copulative

2

small

strongly

with

built,

No

the

traces

of

rather

joints

the

at

a

5th

smaller than

appendage comparatively

Caudal rami

notches.

and somewhat thickened
denticles.

of which, as in

last

of the

ramus being only provided with 3

structure as in the female, each

Antennae

setae.

of

composed

in

expanded,

extremity,

pair

the

of

legs

which

the
is

present.

preceding species,

with the terminal lobes less produced.

Colou: of the living animal not yet assertained.

Length

of adult female

Remarks.

The precent

specimens taken

the

in

1.20

mm.,

species

Baltic,

east

by

its

much

It

inferior

may
size,

male 0.80

mm.

was described by Giesbrecht from some
of Langeland, and sent to him from

Moebius, who had previously recorded
Dance, Claparede.

of

this

form under the name of Monstrilla

easily be distinguished from the preceding species

and more particularly by the rather

different

shape