GUIDE

TO THE

CRUSTACEA, ARACHNIDA,
(CHOPHORA avo MYRIOPODA f

EXHIBITED IN

& DEPARTMENT OF ZOOLOGY,
DRITISH MUSEUM (NATURAL HISTORY),

CROMWELL ROAD, LONDON, S.W.

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TN Gases
CRUSTACEA, ARACHNIDA,
ONYCHOPHORA snp MYRIOPODA
et Es DMPA EL MEINE OH ZOOLOGY:
BRITISH MUSEUM (NATURAL HISTORY),

CROMWELL ROAD, LONDON, 8.W.

WITH 90 ILLUSTRATIONS.

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—_————

Turis Guide deals with the specimens which are exhibited in the
Southern half of the ‘Insect Gallery.’ The great group
Arthropoda, or animals with jointed legs and (usually) a hard
exoskeleton, are here considered, with the exception of the Insects,
which are described in a separate Guide. The present work is
thus concerned with the Crustacea, mainly aquatic in habit, and
represented by familiar animals such as Shrimps, Lobsters and
Crabs; with the Arachnida, the Scorpions, Spiders, Ticks and
their allies; with the Onychophora, constituted by the singular
animal known as Peripatus; and with the so-called Myriopoda,
including the Millipedes and Centipedes.

The section on the Crustacea is written by Dr. W. T. Calman,
that on the Arachnida and Myriopoda by Mr. A. 8. Hirst, and the
portions dealing respectively with the Onychophora and with the
Pentastomida (the latter regarded as degenerate Arachnida) by
Mr. F’. Jeffrey Bell.

Mr. R. I. Pocock, who was formerly in charge of the Arachnida
and Myriopoda, and whose responsibility then included the arrange-
ment of many of the specimens now exhibited, has been kind
enough to read the proof-sheets dealing with those groups.

The thanks of the Museum are due to Messrs. A. and C. Black
for their permission to use certain blocks from Part vii (Dr. Calman’s
volume on Crustacea) of the “Treatise on Zoology,” edited by
Sir Ray Lankester, K.c.B., F.R.S., who has also given his sanction
to their use in this Guide-Book. Figs. 10, 11, 13, 15, 18-22, 26,
27, 30 are derived from this source.

SIDNEY F. HARMER,
Keeper of Zoology.

British Musrum (NaruraL History),
CROMWELL Roap, Lonpon, S.W.

February, 1910.

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TABLE OF CONTENTS.

DEFINITION AND SUBDIVISIONS OF ARTHROPODA
PLAN OF THE GALLERY

Crass 1—CRUSTACEA

Parasitism and Adaptations to Environment
Classification of Crustacea .
Sub-Class—BRANCHIOPODA
Order—PHYLLOPODA
Sub-Order—ANOSTRACA

on NovTostTRAca
a COoNCHOSTRACA

Order—CLADOCERA .

Sub-Class—OSTRACODA

55 COPEPODA
Order—EUuCcoPpEPODA
BD BRANCHIURA

Sub-Class—CIRRIPEDIA
Order—THORACICA .
Sub-Order—PEDUNCULATA
Rs OpERCULATA
Order—RHIzZOCEPHALA
Sub-Class—M ALACOSTRACA
Series—LEPTOSTRACA
Division PHYLLOCARIDA
Series—HUMALACOSTRACA
Division—SyNCARIDA

- PERACARIDA
Order—MysIDAcKEa .

5 CUMACEA

se TANAIDACEA

+3 Tsopopa

PAGE

6 Table of Contents.

. Sub-Order—ASELLOTA .

i PHREATOICIDEA .
on F'LABELLIFERA

FA VALVIFERA

x ONISCOIDEA

i. EPICARIDEA

Order—AMPHIPODA
Sub-Order—GAMMARIDEA
3 HYPERIIDEA
F $5 CAPRELLIDEA
Division—HopLocaRIDA
Order—STOMATOPODA
Division—HUCARIDA
Order—EUPHAUSIACEA
Pe DECAPODA
Sub-Order—Macrura
Tribe—PENAEIDEA
se STENOPIDEA
7 CARIDEA : :
, AsvractpEa (Nephropsidea)
», Lorrcara (Scyllaridea)

5 EXRYONIDEA
35 THALASSINIDEA
Sub-Order—ANOMURA . ;
Tribe—PAGURIDEA
. GALATHEIDEA

3 HIppIpEA
Sub-Order—BRrACHYURA
Tribe—DRoMIAcKA
, OXYSTOMATA
5 OXYRHYNCHA .
56 CYCLOMETOPA
3 CATOMETOPA

Crass 2. —TRILOB ERA

Crass 3.—ARACHNIDA

Sub-Class—EU ARACHNIDA
Division—D&ELOBRANCHIA
Order—XIPHOSURA .
55 GIGANTOSTRACA : :
Division—HKMBOLOBRANCHIA .. a
Order—ScorPiongs .
7 PEDIPALPI

PAGE

or Sr Or Or Or
OODWH eK KH ©

Sr Or Or St Or

We}

Lable of Contents. 7

PAGE

Sub-Order—Uropyar . ; : : . , $7
Tribe—URotTRIcHA . ; : 4 ; : 87

i TARTARIDES . ; : F : : 89
Sub-Order—-AMBLYPYGI s . : , 89
Order—PALPIGRADI . : ; : , : ; 90
5 ARANEAE . 4 : : : : ' 91
Sub-Order—MrsorHEeLak ? ; : ; 7 93

a OPISTHOTHELAE . ; : 3 : 94
Tribe—MyGALOMORPHAE. : : ; : 94

», ARACHNOMORPHAE . . ; : ; 96
Order—So.LiruGak . : F , : : 102
Fy PSEUDOSCORPIONES ‘ : A : 104
Sub-Order—PANCTENODACTYLI ; ; : : 106

< HEMICTENODACTYLI — . : , 106
Order—PopoGona . . : é ; : . 106
% OPILIONES . . ; . ; : 107
Sub-Order—LaANIATORES ; ; 107

si PALPATORES : : : : , 108

a ANEPIGNATHI : : : : : 108
Order—AcaArI . é J ; ; ; 109
Sub-Order—NovostiIGMATA . , : . : 109

55 CRYPTOSTIGMATA . : F ; ; 110

33 METASTIGMATA . : : : 110

PA PROSTIGMATA . : : ; ; 111

FY ASTIGMATA L : 5 : : 113

a VERMIFORMIA : ie : . 114

a TETRAPODA : . ; : ; 114
Sub-Class—PYCNOGONIDA (PANTOPODA) . Pee lel
(Appendix to Arachnida) PENTASTOMIDA . : ; La
Ciass 4—ONYCHOPHORA . . « Yell
Crass 5: —DIPLORODA: = 2 120
Sub-Class—PSELAPHOGNATHA : : : 120
4 CHILOGNATHA : : ; : 121
Order—ONISCOMORPHA : : : é 121
es LIMACOMORPHA : : : i : UD

as HeELMINTHOMORPHA : : ; j 122
Sub-Order—LystoPETALOIDEA ‘ . 122

5 COLOBOGNATHA . : 2 5 mlb,

6 CHORDEUMOIDEA ; é ; ; 122

Fr TULOIDEA . : 5 : ; ‘ 123

5 POLYDESMOIDEA . ; : : 123

8 Table of Contents.

Ciass 6,—PAUROPODA
Cuass 7.—SYMPHYLA

CLass 3—CHITOROD-
Sub-Class—A RTIOSTIGM A

GEOPHILOMORPHA .
ScOLOPENDROMORPHA
CRATEROSTIGMOMORPHA .
7 LITHOBIOMORPHA .

Sub-Class—_ANARTIOSTIGMA

Order

99

PAGE
125

124

GUIDE

TO THE

CRUSTACEA, ARACHNIDA,
ONYCHOPHORA AND MYRIOPODA.

THE specimens exhibited in the “ Insect” gallery belong to the
comprehensive group ARTHROPODA, of which the animals usually
known as Insects form only one of the divisions.

The Arthropoda may be defined as animals in which the body
is more or less distinctly segmented, generally with a firm external
skeleton, and with jointed limbs, some of which are modified to
Serve aS Jaws.

The group is divided, according to the system of classification
followed in arranging the gallery, into six Classes :—

Class 1.—Crustacea (Crabs, Lobsters, ete.).
a Prlo bite.
3.—Arachnida (Spiders, Scorpions, ete., with
Appendix, Pentastomida).
,, 4.—Onychophora (Peripatus).
5.—Diplopoda (Millipedes).
,, 6 —Pauropoda.
,, ¢.—Symphyla.
, 8—Chilopoda (Centipedes).
9.—Insecta (Moths, Flies, Beetles, etc.).

MyRIopopDa.

The Insecta are arranged in the northern half of the Gallery,
and are described in a separate Guide. The remaining classes
occupy the southern half of the Gallery, and are dealt with here
in the order given above.

ol L

West Entrance. Kast Entrance.
coer | 22
i Chilopoda Pauropoda. Diplopoda
. Symphyla. Io golek te
28
~ 25 y Uy 26
Opiliones. Acari, 3 Acari. Pycnogonida.
xq
Pseudo- "AGRE
Podogona. scorpiones Solifugae. A Denes:
24 a ;
21 A 22
Pedipalpi. Palpigradi. hH Araneae.
= i tH
oS)
£corpiones. =a Scorpiones. Gigantostraca.
20 aes
a
17 2 18
Trilobita. Ny; Xiphosura.
Eurypterus.
Brachyura. \\ Brachyura.
16 2 15
FS 13 : 14
iS) Brachyura. : Brachyura.
fe
© :
S :
lan) =
& Brachyura. Anomura. <q Macrura.
12 eal 11
oO 10
Macrura. <i Macrura.
ee — = SS
Euphausiacea. Stomatopoda. 2 Amphipoda.
8 ss 7
5 aa a
Lower Malacostraca. ) Tanaidacea, Tsopoda.
6 : 1
Cirripedia. : Cirripedia.
4 = 3
5 2
1 5 2
Branchiopoda. Ostracoda. NY Copepoda.
3

South Entrance,

PLAN OF SouTH Har or “‘INsect GALLERY,’’ SHOWING POSITION OF CASES
OCCUPIED BY GROUPS DEALT WITH IN THIS GUIDE.

Definition of Crustacea. lial

Class 1.—CRUSTACEA.

INTRODUCTORY.

The exhibited series of Crustacea occupies the southern part of
the “Insect Gallery.” The Table-cases Nos. 1-16 contain a series
of typical representatives of the various Sub-classes and Orders
composing the Class, arranged in systematic order. The Wall-
Cases Nos. 1-6 contain exhibits illustrating the structure and
life-history of the Lobster, and forming an introduction to the study
of the Crustacea; a number of specimens illustrating the habits
and mode of life of various Crustacea; and sundry specimens
which, by reason of their size, could not conveniently be exhibited
in their proper places in the systematic series.

DEFINITION OF CRUSTACEA.

The Class Crustacea, as understood by modern zoologists,
comprises the forms commonly known as Crabs, Lobsters, Cray-
fish, Prawns, Shrimps, Sandhoppers, Woodlice, Barnacles, and
Water-Fleas, besides a multitude of related forms undistinguished
by any popular names. It does not include the King-Crabs
(Xiphosura) and Sea-Spiders (Pycnogonida), formerly associated
with it, but now regarded as more closely related to the Arachnida.

The Crustacea differ so widely among themselves that it is
very difficult to give a definition of the group which will apply to
all its members, and it is hardly possible to do so without entering
into highly technical details of structure and development which
would be out of place here.

It may be said, however, that they differ from Insects,
Arachnida, and the other groups which, together with Crustacea,
form the comprehensive group (Phylum or Sub-Phylum) Arthro-
poda, in having two pairs of antennae (feelers) in front of the

Wall-
cases
Nos. 1-3.

12 Guide to Crustacea.

mouth and at least three pairs of jaw-like appendages behind the
mouth, in being nearly always of aquatic habits, and in breathing »
by gills or by the general surface of the body.

A Crustacean can usually be distinguished from any other
Arthropod by the fact that its ‘“walking-legs”’ do not correspond
in number or arrangement with those found in the other groups
Thus an Insect can usually be recognised at first sight by having
three pairs of legs, an Arachnid by having four pairs, and a
Centipede or a Millipede by having a great number of legs, all
nearly alike. The Crustacea, on the other hand, show a great
variety in the arrangement of their walking or swimming legs, but
they very seldom exhibit any special resemblance, in respect of
these appendages, to the other large groups of Arthropods.

THE LOBSTER AS A TYPE OF CRUSTACEA.

The plan of structure common to the whole Class will be best
understood by beginning with the study of a typical form.

For this purpose the common Lobster has been selected as
being easily accessible, of convenient size, and not too specialised
to admit of ready comparison with other Crustacea.

The Crayfish, which is the type more usually described in
text-books, differs only in minor details from the Lobster.

Like the other Arthropoda, the Crustacea have the body and
limbs encased by a firm covering which gives support to the soft
internal organs and in particular affords points of attachment for
the muscles by means of which the animal moves. In other
words, this covering plays the part of a skeleton; but since, unlike
the bony skeleton of Vertebrate animals, it is outside instead of
inside the soft parts, it is distinguished as an “exoskeleton.” In
many Crustacea also, the exoskeleton is sufficiently strong to serve
the purpose of defensive armour, and to enable the limbs to act as
efficient and powerful weapons.

Although the firm outer covering is really continuous over the
whole of the surface of the body and limbs, it becomes thinned away
in places to form joints permitting movement between the various
parts. Thus, the body and limbs are divided into ‘‘ segments ” *

* The word “ joint,’ often applied to these divisions of the body and
limbs, ought properly to be restricted to the hinge or connection between two
segments.

The Lobster as a type of Crustacea. 13

which, in the case of the body, are termed body-segments or
“somites.”

A study of the various modifications of structure presented by Wall-
Crustacea and other Arthropoda has led to the conclusion that Near
they are to be regarded as built up of a series of somites or body-
segments, which may be distinct or soldered together, and each of
which bears typically a single pair of limbs or appendages.

Thus, in the Lobster (Fig. 1), the hinder half of the body (or
abdomen) is plainly made up of six somites (besides a tail-piece or

Al-dornen Cenhalothorax

: ye
Somites Carapnace | :
ervical groove | Rostrum

Antennule

6 EY ye : za oa
“oy a 7 WS Dy § mon : Wy = 3 ; SE ea %
Tail

Pleonods

N Swim merets )
Vronoe

Cheliped *
(First leg)

Walking legs

ines ale

The Common Lobster (Homarus gammarus). Female, from the side.
[Wall-case No. 1.]

“telson”’), each of which carries on the under side a pair of
“ swimmerets.” The front half of the body is not so divided, but
is covered by a large shield or ‘‘ carapace’ which projects between
the eyes as a toothed beak or “rostrum.” Since, however, this
part of the body also bears a number of appendages constructed
on the same plan as the swimmerets of the abdomen, it is con-
cluded that here also we have to do with a series of somites,
although they are so completely fused together as to be indistin-
guishable except by their appendages. That this conclusion is
correct is proved by comparison with some of the lower Crustacea,
for instance, Anaspides (see Table-case No. 5), in which there is no

Wall-
cases
Nos. 1-3.

14 Guide to Crustacea.

carapace, and the fore part of the body has eight distinct somites
each bearing a pair of walking legs. In front of these eight
somites, which form what is called the “ thorax,” is the “ head,”
a part of the body which is never, in any Crustacean, distinctly
segmented, but which, since it bears five pairs of appendages,
must contain at least five somites. The part of the body covered
by the carapace of the Lobster includes the head and the thorax
and is known as the “ cephalothorax.” It is necessary to remark,
however, that the regions of the body named head, thorax, and
abdomen in the Crustacea are by no means exactly equivalent to
those so named in the other Arthropoda, for instance in Insects,
and still less to the parts bearing
the same names among Vertebrate
animals.

This “segmentation” of the
body, or division into somites, is
not only shown by the external
covering, but affects some of the
internal organs as well. Leaving
these aside for the present, how-
ever, and considering only the
exoskeleton, the structure of a

typical somite will be best un-
ce Perc aetna eee derstood by examining one of the
separated and viewed from in separated abdominal somites of the
pron LWall-case Now| Lobster (Fig. 2). This consists of
a ring of shelly substance, connected
with the rings in front and behind by areas of thin membrane
which permit movement in a vertical plane. For convenience
of description the upper or dorsal part of this ring is called
the “‘tergum”’ (or ‘“‘tergite’’) and the under or ventral part the
“sternum” (or “sternite’’). To the sternum are attached the
appendages (or swimmerets), while the tergum overhangs the
base of the appendage on each side as a flap called the
‘‘pleuron.” The terminal segment of the body or “ telson” never
bears typical limbs, and on this account and also because of
its mode of development in the embryo, it is not regarded as a
true somite.

The carapace of the Lobster is not formed simply by the terga of
several adjacent somites becoming soldered together. This is
shown by a comparison with some of the lower shrimp-like
Crustacea (Mysidacea, see Table-case No. 5), in which the carapace

Séermum
Fie. 2.

Lobster—A ppendages. 15

is seen to arise, as a fold of the skin, from the hinder edge of Wall-
the head-region, and to envelop the distinctly segmented thorax Nance
like a loose jacket. In the Lobster, this fold has coalesced, down

the middle of the back, with the terga of the thoracic somites, but

at the sides it hangs free, enclosing a “ branchial cavity’ in which

the gills he between it and the side of the body. The free part

of the carapace which covers the branchial cavity is known as the

“‘ branchiostegite,’ and its front end is marked off on the outside

of the carapace by an oblique “ cervical groove”’ (Fig. 1), which

has been supposed to indicate the limit between the head and the
thorax,

Appendages.—Excluding the movable stalks on which the
eyes are set and of which the nature will be discussed later, the
body of the Lobster carries nineteen pairs of appendages. In front
of the head are two pairs of feelers, the “ antennules”’ and
‘‘antennae’’ respectively (sometimes called the first and second
antennae) ; near the mouth are three pairs of jaw-appendages, the
strong “ mandibles” and the flattened leaf-like “ maxillulae” and
“maxillae”’; following these, which belong to the head-region, are
three pairs of thoracic appendages, the ‘ maxillipeds,” which form
a transition between the true jaws and the legs. The large claws
and the four pairs of walking legs may simply be termed “ legs,”
and together with the three pairs of maxillipeds, correspond with
the eight somites of the thorax already referred to. The six
somites of the abdomen have each a pair of appendages, those of
the first five being known as swimmerets (‘‘ pleopods ’’), while
those of the last somite are known as the “ uropods,” and are large,
flattened appendages spread out on each side of the telson to form
the tail-fan. All these appendages can be shown to be constructed
on a common plan, which is seen in a simple form in the case of
the swimmerets. Hach of these consists (Fig. 2) of a stalk, the
“ protopodite,” with two branches known respectively as the
“endopodite” (on the inner side) and the “ exopodite”’ (on the
outer side). The protopodite itself is composed of two segments ;
the first, very small, is the “ coxa,’ and the second, much larger,
is the ‘ basis.” |

If the other limbs be compared with the swimmerets it will be
found that they can be derived, without much difficulty, from the
simple type. The antennules (Fig. 1), which appear most simple,
are perhaps the least easy to interpret. Although they plainly
consist, like the swimmerets, of a stalk and two branches, there are
reasons for doubting whether these three parts correspond with

Wall-
cases
Nos. 1-3.

16 Guide to Crustacea.

the protopodite, exopodite, and endopodite respectively. In the
antenna, on the other hand, there is little difficulty in recognising
the two segments of the protopodite, the exopodite reduced to a
small movable plate or scale, and the endopodite drawn out into
a long lash or flagellum of very numerous small segments.

The mouth-parts will be best understood by comparing them
in order from behind forwards, beginning with the third maxilliped
(Fig. 3). In this appendage it will be seen that the second
segment of the protopodite carries an exopodite which ends in a
lash or flagellum of numerous segments, and an endopodite of
five segments which forms the main part of the limb. In addition
to these divisions, however, there is another part not present in the
swimmeret which we have taken as the type. This is the “ epi-
podite,” a membranous plate attached to the outer side of the first
segment (coxa) of the protopodite,
and bearing one of the gills (to be
described later) attached to it.
The second maxilliped is not dis-
similar in structure, though much
smaller than the third, but the
first maxilliped differs considerably —
from both. The same parts can

Eninodite be recognised in it, but the

Fra. 3. endopodite is shorter than the

Third maxilliped of Lobster. @XOpodite and has only two seg-
[Wall-case No. 1.] ments; and the two segments of

the protopodite grow out on their
inner side into two large plates, fringed with bristles and
serving as jaws. In the mazilla (second maxilla), these jaw-
plates (‘ gnathobases’”’) are still more developed and each is
slit into two. The endopodite is small and unsegmented,
while on the outer side is a large plate which is probably the
exopodite, although some have regarded it as the epipodite.
Whatever its nature, this plate has an important function, since it
lies in a channel leading forwards from the gill-chamber and
serves by its continual movements to keep a current of water
flowing over the gills. The mazxillula (first maxilla) consists of
little else than the two gnathobases, here undivided, and a small
endopodite. The strong mandibles are clearly the chief instru-
ments in the mastication of the food, to which the other mouth-
parts are only accessory. Each consists of a massive “ body”
which seems to represent the first segment of the protopodite

Lobster—A ppendages, Anatomy. 17

with its gnathobase, and a small “palp”’ of three segments Wall-
representing the rest of the protopodite with the endopodite. Need

The rest of the appendages may be briefly disposed of. The
walking-legs (Fig. 1) can easily be seen to correspond, segment for
segment, with the third maxillipeds, except that they have no
exopodites. The large claws (chelipeds), like the two pairs of legs
immediately succeeding them, are chelate or pincer-like. This
modification, which is very frequent among Crustacea in limbs
used for seizing food, is brought about by the penultimate segment
of the limb growing out into a process, the ‘‘ immovable finger,”
lying alongside the last segment, which can be brought into con-
tact with it and is known as the ‘‘ movable finger.”

The movable stalks, upon which the eyes are set, are divided
into two segments and in a few Crustacea they are even composed
of three. The view was long and widely held that these stalks
were the equivalent of a pair of appendages like the legs or jaws.
There are some reasons, however, for believing that this is not the
case, and the eye-stalks are therefore omitted from the list of
the Lobster’s appendages given here.

Some of the gills (branchiae) of the Lobster are seen attached
to the epipodites of the thoracic limbs. Their exact arrangement,
however, is more clearly shown by the preparations in spirit
exhibited alongside. In a transverse section through the thorax
it is seen that the gill attached to the epipodite of the leg lies on
the outer side of the branchial chamber. It is known as a
“podobranchia.”’ Next to it on the inner side are two gills which
spring not from the leg itself, but from the membrane of the joint
between the leg and the body. These are called ‘“ arthrobranchiae.”
Finally, next the inner wall of the chamber, is a gill attached to the
wall of the body itself and known as a “ pleurobranchia.” The
complete set of four gills is not present on every thoracic somite
and the arrangement differs very much in different Crustacea.

Internal Anatomy.—The general arrangement of the internal
organs of the Lobster is shown by a preparation in which the
animal is dissected from the side (Fig. 4). The alimentary canal
begins with a short gullet or “ oesophagus’ leading upwards from
the mouth into the large “stomach,” from which the “intestine ”
runs straight backwards to the vent on the under side of the
telson. The stomach is not very suitably named, for it is probably
not the place where the chief processes of digestion go on, but on
the other hand it contains a complex apparatus known as the
“oastric mill” which acts as a gizzard in grinding up the food.

Cc

18 Guide to Crustacea.

Wall- It is divided into two chambers, a larger one in front, the “ cardiac
ee 5 chamber,” which serves as a kind of crop, and a smaller “ pyloric
os. L-o.

chamber” behind. In the narrow opening between the two
chambers are set three strong teeth which are connected with a
system of plates and levers lying in the stomach-wall and moved
by special muscles. This development of hard plates and teeth is
associated with the fact that the whole stomach is lined by a
membrane continuous at the mouth with that which covers the
surface of the body and becomes thickened and hardened to form
the shell. The external membrane also becomes turned in at the
vent to line a considerable part of the intestine.

On each side of the thoracic region of the body is a large

Opening of Liver-duct
Optic Nerve. \ Heart
\ Brain bi
‘\.\ Stomach \

Antennular Nerve ~~ Jy
#5 (\
EDI NS X

ARS
Sea

Superior abdominal artery
! Intestine

Muscles of
abdomen

! i} °
5, | Ventral Nerve-chain
1 Vas deferens

Descending artery

Vent *

; No pe

FirstGanglion of |

Ventral Nerve-chatn
Fig. 4.

Dissection of male Lobster, from the side. [Wall-case No. 1.)

glandular mass, the “liver” or digestive gland, which opens into
the alimentary canal by a short duct on each side just behind the
stomach.

The heart lies near the back, just under the hinder part of the
carapace. It gives off a number of large arteries in front and
behind, as well as one (‘‘ descending artery’) which runs down-
wards to the sternal surface of the thorax. As in other Arthro-
poda, there are no distinct veins, but the blood is discharged from
the smaller arteries into the general cavity of the body and finds
its way by ill-defined venous channels, first to the gills, and from
these to the “ pericardium ”’ or space surrounding the heart. From
the pericardium the blood returns through six valvular openings
into the heart itself.

The excretory system (corresponding in function with the

Lobster—A natomy, Sexes. 19

kidneys of the Vertebrate animals) is represented by a pair of Wall-

glands known as the “ green glands” lying at the sides of the head ¢@ses
: . > fo)

and opening to the exterior each on a small tubercle on the first

segment of the antenna.

The central nervous system consists of a “ brain,” lying in front
of the head, connected by a pair of cords which pass on either
side of the gullet with the “ventral nerve chain” in which may
be distinguished twelve nerve centres or ganglia.

The eyes, as already mentioned, are set on movable stalks.
The black, kidney-shaped area at the end of the stalk can be seen,
under a magnifying lens, to be divided into numerous minute
facets (some 13,500 in number), for the most part square in
outline. It is not correct to state, as is sometimes done, that each
facet corresponds to a separate eye, forming a separate image of
the object looked at; the whole assemblage of facets and the
structures underlying them co-operate to form a single image on
the receptive nerve-endings in the interior of the eye.

In the basal segment of the antennule is the so-called auditory
“organ, 2 small pouch open to the exterior and containing in its
cavity a number of grains of sand. This pouch, which has on its
inner surface numerous feathered hairs connected with a large
nerve, was formerly regarded as the Lobster’s ear. Although it is
not impossible that it may have to do with the sense of hearing,
recent investigations have shown that its principal function is
connected with maintaining the equilibrium of the body in walking
or swimming.

The dissection exhibited (see Fig. 4) is one of a male Lobster,
and the testis can be seen lying below the heart and giving off a
duct, the vas deferens, which opens to the exterior on the coxa of
the last pair of legs.

Differences between the sexes.—T'wo preparations are
exhibited in order to show the chief external differences between
the sexes of the Lobster (Fig. 5). The most easily noticeable
differences are the greater breadth of the abdomen and the larger
size of its side-plates in the female than the male. The first pair
of swimmerets (which, unlike the other pairs have only one branch
in both sexes) are very slender in the female, but are much larger
and peculiarly shaped in the male. The second pair have an
additional lobe on the inner side of the endopodite in the male.
The openings of the genital ducts can be seen on the first segment
(coxa) of the last pair of walking legs in the male, and on that of
the last pair but two in the female. Finally, the female has on

c 2

1-3.

Wall-

cases

Nos. 1-:

2

.

20 Guide to Crustacea.

the under surface of the thorax, between the last two pairs of legs,
a curious three-lobed structure with a slit-like opening in the
middle, known as the “ sperm-receptacle.”

As in most Crustacea, the eggs are carried, after spawning, by
the parent Lobster, and, as in most of the higher Crustacea
(Decapoda), they are attached to the swimmerets on the under

Male. Female.

1M, OE

Male and Female Lobsters, showing the difference in the relative breadth
of the abdomen in the two sexes. This figure also illustrates the dis-
similarity of the large claws and the fact that the large ‘‘ crushing-claw ”’
may be on either the right or left side of the body. [Wall-Case No. 1.]

surface of the abdomen. The female Lobster carrying spawn in
this way is said by fishermen to be ‘in berry.” A specimen in
this condition is shown in spirit, and a drawing, in natural colours,
is hung in the upper part of the Case. The number of eggs carried
by a single Lobster may vary from about 3,000 to nearly 100,000.

Development.—Like most other Crustacea, the Lobster
when hatched from the egg differs considerably in form from the

oo

Lobster —Development, Moulting. 21

adult animal. An enlarged drawing of this stage is hung in Wall-

Wall-case No. 2. The most important differences from the adult a 3

are the absence of all the abdominal appendages (pleopods and
uropods) and the presence on each of the legs of an exopodite.
These exopodites are fringed with hairs and are used as swimming
organs, by means of which the larvae move rapidly about at the
surface of the sea. Ata later stage (see drawing), the exopodites
of the legs are lost and the young animal, which has now assumed
the essential structure of the adult, sinks to the sea-bottom. In
many Crustacea the changes of form between the larval and the
adult state are much greater than they are in the Lobster, but
in some cases they are less marked, and the animal is hatched in
what is practically the adult form.

‘Moulting.—As already mentioned, the outer covering of the
Lobster is quite continuous over the whole surface of the body
and limbs. It consists of a substance known as “ chitin,’ which
resembles horn and is hardened by the deposition of lime-salts to
form the shelly parts of the exoskeleton. At the joints the covering
is thin and soft and contains no lime. As this covering will not
stretch to any great extent, the Lobster, like all other Arthropoda,
requires to cast its shell at intervals as it grows. In this process
of moulting (or ecdysis) the integument of the back splits between
the carapace and the first abdominal somite; and the body and
limbs are gradually withdrawn through the opening, leaving the
east shell with all its appendages almost entire. The new shell,
which had been formed underneath the old before moulting, is at
first quite soft, and the animal rapidly increases in size by the
absorption of water. The shell gradually becomes hardened by
the deposition of lime-salts.

Several series of specimens illustrating the process of moulting
are exhibited in Wall-case No. 3. These have been prepared and
presented to the Museum by Mr. and Mrs. H. J. Waddington, of
Bournemouth, who have been very successful in keeping marine
animals alive for long periods in aquaria. ‘Two cast shells, obtained
successively from a single Lobster, and the Lobster itself preserved
in the “soft”? condition immediately after escaping from the
second of these, show very clearly the increase in size at each
moult, and the same point is illustrated in a different way by a
drawing hung in this case, in which are superposed the outline of
a Lobster before moulting and the outline of the same animal a
few hours after the moult.

In a jar in the centre of the case are shown several specimens

Wall-
cases

Nos. 1-3.

Guide to Crustacea.

F1G.. 6.

Series of cast shells obtained from a single
individual of the Shore-Crab (Carcinizus
maenas) kept in an aquarium.
carapace of the largest is about 24 inches

wide.

[ Wall-Case No. 3.]

The

of the Edible Crab, of which
one is in the act of moulting.
The carapace has become
separated from the abdomen
and legs, and the body is
beginning to be withdrawn
from it.

On the right of the case is
a series of cast shells obtained
froma single individual of the
Shore-Crab (Fig. 6). The crab
was captured on 14th May,
1901. It was then in the
second larval or Megalopa
stage, and was found swimming
at the surface of the sea. It
lived in Mr. Waddington’s
aquarium till 20th July, 1904,
and during that period it
moulted seventeen times. All
the castshells, except two which
were destroyed by accident, are
exhibited.

In the lower part of the
case two very beautiful series
are exhibited, each obtained
from a single Lobster in Mr.
Waddington’s aquaria, and to-
gether they give an almost
complete picture of the growth
of the animal from an early
post-larval stage until it reaches
amarketable size. The younger
series begins with a specimen
of about +ths inch length of
body, which moulted on 21st
August, 1906; the latest of the
fourteen moults exhibited was
obtained on 8th June, 1909,
when the animal was about
41 inches in length. The second
series begins with a specimen

Asymmetry, Effect of Parasites. 23

of about 45 inches long, obtained on 16th September, 1904. Wall-

Between that date and 31st July, 1909, when the lobster died, it Noe ies

moulted seven times and grew to a length of 9 inches.

Asymmetry.—A point on which information is often asked,
the unlikeness in size and shape of the great claws of the Lobster
and other Crustacea, is illustrated by specimens in Wall-case No. 1.
In the preparations of the male and female Lobster (Fig. 5), for
instance, or in the pair of claws from a very large Lobster in the
lower part of the case, it will be seen that one of the claws is
more massive than the other and that the fingers are armed with
blunt knobs. It is, in fact, used for crushing the shells of animals
on which the Lobster may be feeding, and is known as the
“ erushing-claw.” The other is more lightly built, with sharp saw-
like edges to the fingers, and is known as the “ cutting-claw.”
There is no rule as to the side of the body on which either form
of claw is found, ‘ right-handed” and “ left-handed” specimens
being about equally common. In others of the higher Crustacea
the disparity in size of the two claws is much greater than in the
case of the Lobster. This is shown by the claws of the large
Tasmanian Crab (Pseudocarcinus gigas), of which a pair is
exhibited in the lower part of Wall-case No.1, and other examples
will be found in the table-cases. In some crabs the larger claw
is more or less constantly on the same side of the body; that
is to say, right-handed (or, more rarely, left-handed) individuals
predominate.

Occasionally, in the Lobster, specimens with similar claws
occur. Most commonly, in these, both claws are of the cutting
type, but, very rarely, specimens like that shown in the lower
part of Wall-case No. 1, are found in which both claws are of the
crushing type. The mode of production of such abnormalities is
not fully understood, but it seems probable that in most cases it is
associated with the regeneration of limbs removed by accident or
thrown off after injury.

MODIFICATIONS CAUSED BY PARASITES.

A series of specimens, exhibited in Wall-case No. 2, illustrate the
changes of structure produced in certain crabs which are infested
by the degenerate Crustacean parasite Sacculina. It is a curious
and significant fact that these changes affect almost exclusively

Wall-
cases

Nos. 1-3.

Wall-

cases

Nos. 1-6.

24 Guide to Crustacea.

the secondary sexual characters of the crabs. The details of the
modifications are explained at length in the labels accompanying
the specimens, and need not be recapitulated here ; but it may be
said in general that the characters distinctive of either sex, e.g.,
the large chelipeds of the male, or the egg-carrying appendages of
the abdomen in the female, become reduced in infected specimens,
and that in some cases the male may even assume the characters
of the female, although it would appear that females never take on
distinctively male characters.

ADAPTATION TO ENVIRONMENT.

The remaining specimens in Wall-cases 1-6 will, for the most
part, be referred to in describing the systematic series to which
they properly belong. A number of exhibits, however, attempt
to reconstruct the natural environment of the animals, and may
conveniently be mentioned here. It is, of course, very hazardous
to attempt to apply theories of “protective resemblance” to explain
the characters of animals that are preyed upon by, and in turn
prey upon, organisms, of which the sense-organs differ widely
from our own; but it is at all events certain that—to human eyes—
the slender thread-like Caprellids are extremely hard to detect
among the branches of the Hydroid zoophytes to which they cling
(Wall-case No. 4), and that it is very difficult to sort out the little
pebble-like Hbalia (Wall-case No. 6) from the gravel brought up
by the dredge. Still more effective are the disguises assumed by
certain crabs of the tribe Oxyrhyncha, and illustrated by the
specimens of Macropodia, Maia, and Hyas in Wall-case No. 6. In
these crabs the surface of the body and limbs is covered by a mass
of living seaweeds, sponges, and zoophytes, which render the
animals almost invisible when they crouch motionless at the
bottom of a rock-pool. It has been found that when this covering
is removed artificially, or when after moulting the surface of the
body is clean, the crab actually plants little fragments of seaweed
and the like on its own back. The fragments are held in place by
hooked hairs on the surface of the body, and they continue to grow
and thrive in their new position.

Classification. 20
SYSTEMATIC SERIES. Table-
cases

The following table gives the system of classification which has Nos. 1-16.
been adopted in arranging the collection :—

Class CRUSTACEA.
Sub-class BRANCHIOPODA oer eae
+5 adocera.
», | Myodocopa.
,, Podocopa.
,, Hucopepoda.
Branchiura.

~S
!
|, OSTRACODA ae
| » Choracica.

F CORMPODA

,, Acrothoracica.
, Ascothoracica,
» Apoda.
5, Rhizocephala.
S MALACOSTRACA.
Series LEPTOSTRACA.
Division Phyllocarida . Order Nebaliacea.
Series HUMALACOSTRACA.
Division Syncarida . . Order Anaspidacea.
» Mysidacea.
,» Cumacea.
“ Peracarida , Tanaidacea.
», Isopoda.,
,, Amphipoda.
- Hoplocarida. 5, stomatopoda.
Kuphausiacea.
» Decapoda.

5 CIRRIPEDIA

_ Hucarida

.
oo’

Sub-class I.—BRANCHIOPODA.

This Sub-class includes a number of very primitive Crustacea Table-case
which differ widely from one another in many points of structure, NC
but agree in having the appendages of the trunk, for the most
part, flattened and leaf-like. It is divided into two Orders,
Phyllopoda and Cladocera.

Order 1.—Phyllopoda.

The number of somites is large (about 14 to 40) and the trunk-
appendages may be still more numerous (up to 60), several pairs being
sometimes borne on each somite in the posterior region of the body.

The Phyllopoda are specially interesting on account of their

Table-case

No. 1.

26 Guide to Crustacea.

primitive characters. In the large number of the somites and the
uniformity of the limbs, as well as in some points of internal
structure (heart, nervous system) they approach more closely
than any other living Crustacea to the hypothetical ancestral type
of the Class. In some respects, however, such as the reduction of
the mouth-parts, they are considerably specialized.

The order includes three Sub-orders (sometimes ranked as
Orders) the members of which differ widely in external appear-
ance. ‘They are found in fresh water or in brine pools,

ais We

Apus cancriformis, from Kirkcudbrightshire, slightly enlarged.
Table-case No. 1. |

In the Sub-order AnosTRAcA there is no carapace and the
animals have a more worm-like appearance than is usual in
Crustacea. ‘The eyes are set on movable stalks. The males are dis-
tinguished by the remarkable development of the antennae, which
form complicated clasping organs for seizing the females. This is well
shown in the specimen of Streptocephalus rubricaudatus exhibited.

In the Sub-order Norosrraca the carapace forms a broad
dorsal shield, resembling, at first sight, that of the Arachnidan
King-crabs. <Apus cancriformis (Fig. 7) is found in fresh-water

Branchiopoda. 27

pools and ditches in many parts of Europe, but it is very uncertain Table-case
in its occurrence, and it may suddenly reappear in numbers after N°. !-
an absence of many years. Males are rarely found. It was
formerly found in several localities in the South of England, but
no British specimens were seen for upwards of forty years, and
the species was supposed to be extinct in this country. In 1907,
however, it was discovered by Mr. F. Balfour Browne, in Kirk-
cudbrightshire, and some specimens obtained by him are exhibited.
The eggs of Apus, and indeed of most Branchiopoda, can survive
being dried, and they may be carried from place to place in mud
adhering to the feet of wading birds
or in other ways. There can
be little doubt that the recent
appearance of the species in Scot-
land was due to introduction of
the eggs in some such way from
the Continent.

The species of the Sub-order
ConcHostrRaca have the body
enclosed in a bivalved shell, which

resembles very closely the shells fine, 8
of some Molluscs. The genus

s 3 = 2 : : Estheria melitensis (slightly en-
Hstheria (Fig. 8), of which speci- larged). [Table-case No. 1.

mens are exhibited, is of interest
on account of its geological antiquity; fossils referred to the
genus occur in rocks of the Devonian period.

Order 2.—Cladocera.

The number of somites is small. There are from four to six
pairs of trunk-limbs. The carapace generally forms a_ bivalve
shell, enclosing the body and limbs but leaving the head free.
The antennae are large and two-branched, and are used in
swimming.

The Cladocera are generally very small animals, and from their
jerky mode of swimming have received the name of ‘‘ Water-fleas.”’
They are abundant everywhere in ponds and ditches, and a few
Species are found in the sea.

One of the commonest species in fresh water is Daphnia pulex,
of which specimens are exhibited together with an enlarged draw-
ing of the animal as seen under a low power of the microscope

Bis Guide to Crustacea.

Table-case (Fig. 9). Leptodora kindti is the largest species of the Order. It

No. 1.

is found chiefly in lakes, and its glassy transparency makes it a
very beautiful object when alive. It is exceptional in the small
size of the carapace, which does not enclose the body and serves
only as a brood-pouch.

Fic. 9.

Daphnia pulex. Female carrying eggs in the brood-chamber.
Enlarged. [Table-case No. 1.}

Sub-class II.—OSTRACODA.

The number of somites, as indicated by the appendages, is
smaller than in any other Crustacea, there being, at most, only
two pairs of trunk-limbs behind those belonging to the head-
region. The carapace forms a bivalved shell completely enclosing
the body and limbs. There is a large, and often leg-like, palp on
the mandible. The antennules and antennae are used for creep-
ing or swimming.

Ostracoda, Copepoda. 29

The Ostracoda (Fig. 10) are for the most part extremely Table-case
minute animals, and only one or two of the larger species can be N° 1:

exhibited. They occur abundantly in fresh water and in the sea,
and their fossil remains are found in all geological formations from
the oldest to the most recent. Nearly all the Ostracoda belong to
two Orders, the Myodocopa and the Podocopa, of which the former
may generally be distinguished by a notch (Fig. 10, ”) in the
anterior part of the margin of the shell which is absent in the
latter.

A series of enlarged drawings gives some idea of the diversity
of form and ornamentation in the shells of these minute Crustacea.

1D; 10)

Shells of Ostracoda, seen from the side. A. Philomedes brenda (Myodocopa) ;
B. Cypris fuscata (Podocopa); C. Cythereis ornata (Podocopa) : all much
enlarged. n., Notch characteristic of the Myodocopa; e., the median
eye; a., mark of attachment of the muscle connecting the two valves of
the shell. A. and C. are marine species, B. is from fresh water. (From
Lankester’s ‘‘ Treatise on Zoology,” after Brady and Norman, and Miiller.)

Sub-class III—COPEPODA.

There are, at most, ten free somites behind the head. The
carapace is reduced or absent. The first thoracic limbs form
maxilipeds, and are followed by four or five pairs of two-branched
swimming feet. The posterior region of the body (the so-called
“abdomen’”’) is generally narrowed and is without limbs, but the
terminal segment carries a pair of appendages, forming the
‘caudal fork.”

Many Copepoda are found in fresh water, but the majority
inhabit the sea, where they are often extremely abundant. They
form one of the most important constituents of the “ plankton,”
the assemblage of floating organisms in the waters of the open
ocean. Since it is chiefly on this plankton that all the other
inhabitants of the sea ultimately depend for food, it may be said
that the Copepoda, notwithstanding their small size, play a more

Table-case
No. 2.

Table-case
No. 2.

30 Guide to Crustacea.

important part in the economy of nature than any other
Crustacea.

_ Many Copepoda live as parasites on fishes and other aquatic
animals, and as a result of this parasitic life their structure
becomes greatly modified and degenerate.

The Order Eucopepopa (Fig. 11) includes the great majority
of the Copepoda, both free-living and parasitic. True paired com-
pound eyes are never present, but the median unpaired eye is
often well-developed. Most of the free-swimming species are
extremely minute, few attaining the size of Huchaeta norvegica, of
which specimens are exhibited. The enlarged drawings show the
briliant colours of some pelagic species.

iin

Hire. 11.

Calocalanus pavo, one of the free-swimming Copepoda of the “ plankton.”
Enlarged. (From Lankester’s ‘‘ Treatise on Zoology,’’ after Giesbrecht.)

The parasitic species are usually much larger than those
which live a free life, and a number of species taken from common
fishes are exhibited. Pennella, which is found on whales and
fishes, is the giant of the sub-class, some specimens being even
larger than that exhibited here.

The order Brancuiura includes a small number of fish-
parasites whose exact relations to the other Copepods are obscure.
They possess a pair of compound eyes, and a piercing stylet, con-
nected with a poison-gland, in front of the mouth. <Argulus

foliaceus is common on fresh-water fishes in this country. The

large Argulus scutiformis is taken from marine fishes in Japan.

Cirripedia. 31

Sub-class IV.—_CIRRIPEDIA.

The members of this group are sedentary animals, attached by
the anterior part of the head-region, and having the body generally
enclosed by a fleshy mantle, representing the carapace, strength-
ened externally by shelly plates. There are typically six pairs of
trunk-limbs, each two-branched and many-jointed.

On account of their shelly covering the Cirripedia were classed
by the older naturalists with the Mollusca, and it was only when
their larval stages were discovered in 1829 by J. Vaughan

Ere. 12.

Group of specimens of a stalked Barnacle (Lepas anatifera). One showing
the cirri extended as in life. {Table-case No. 3.|

Thompson, that their affinities with other Crustacea were recog-
nised. Nearly all the Cirripedia are hermaphrodite, having both
sexes combined in each individual, a condition very rare among the
Arthropoda. In some cases, however, there are dwarf male
individuals which pair either with females or with hermaphrodites
of normal structure.

The Sub-class may be divided into five Orders, but three of
these comprise only a few imperfectly-known forms which cannot
be exhibited here.

Table-
cases

Nos. 3 & 4.

Table-case
No. 3.

32 Guide to Crustacea.

Order 1.—Thoracica.

This Order includes the typical Cirripedes, in which the six
pairs of feathery trunk-limbs are well developed. Two sub-orders
are recognised.

In the sub-order Pepuncunata (the Stalked Barnacles) there
is a fleshy peduncle, or stalk of attachment, at the free end of
which is the “capitulum”’ formed by the mantle enclosing the
body and limbs.

Specimens of the common Goose-Barnacle, Lepas anatifera
(Fig. 12), are exhibited showing the external appearance with the

rer.l.-

lane, 18%

A. A stalked Barnacle (Lepas anatifera). B. A sessile Barnacle (Balanus
hameri). p., The peduncle. The other letters relate to the “valves” or
parts of ‘the shell; c., carina; c.l., carino-lateral; /., lateral; 7. + 7.1.,
rostrum and rostro-lateral fused together; sc., scutum; ¢., tergum.
(From Lankester’s ‘‘ Treatise on Zoology,” after Darwin.)

feathery ‘“cirri’’ extended from the opening of the shell; in
another specimen half of the shell is removed to show the form of
the body and limbs within it; and a third preparation shows the
five valves of the shell (Fig. 134) separated from each other. Like
many other barnacles, the species of Lepas are commonly attached
to floating objects, drift-wood, ships’ bottoms, and the like, and
most of the species have an extremely wide distribution in all the
oceans. The great length sometimes reached by the peduncle of
the common goose-barnacle is shown by a fine group of specimens
mounted in a jar by the doorway at the south end of the gallery.
Among the other genera of stalked barnacles exhibited, Polli-

Cirripedia, Barnacles. 33

cipes may be noted as having rows of valves on the capitulum Table-case
which pass gradually into the small scales covering the peduncle. No. 3.
These scales appear to be the remains of a shelly armour covering

the peduncle which was more fully developed in certain extinct
genera, and is shown in the casts of the fossil Loricula and Turri-

lepas exhibited in this case. The genus Scalpellum is of interest

not only on account of the deep-sea habitat of many species and

the great size of some (Scalpellum giganteum), but also and more
especially because of the dwarf male individuals already alluded to,
which are found in this genus and in the related Jbla. In the
different species of Scalpellum three conditions are represented.

In some, all the individuals of a species are similar and hermaphro-

dite as in ordinary barnacles; in others, as in Scalpellum peronii,

of which a specimen is shown, the large hermaphrodite individuals

have small males attached to them like parasites; in others again

the separation of the sexes is complete and the larger individuals

are purely female.

Most barnacles are hatched from the egg as actively swimming
larvae of a type which is found in many other Crustacea, and is
known as the Nauplius. They have three pairs of appendages, an
unsegmented body, and a conspicuous median eye. Like many
other “pelagic” animals the Naupli of barnacles living at the
surface of the ocean often have long spines and outgrowths
from the surface of the body, which are probably of service in
keeping the animals afloat. A coloured drawing of one of these
spiny larvae is exhibited. In its later development the young
barnacle passes into a stage in which the body and limbs are
enclosed in a bivalved shell like an Ostracod. On account of this
resemblance the stage is known as the “ Cypris”’ stage, after one
of the genera of Ostracoda. After swimming about for some time
longer it attaches itself by means of its antennules, casts off
its bivalved shell, and gradually assumes the structure of the
adult.

The Sessile Barnacles or Acorn-shells, forming the sub-order
OprRcuLATA (Fig. 138), agree in most points of structure and
development with the stalked barnacles, but they have no peduncle.
The shelly plates of the mantle are, for the most part, soldered
together to form a cylindrical or conical case, the opening of which
is protected by four movable “ opercular”’ plates. Ina preparation
of Catophragmus polymerus here exhibited, names are attached to
those parts of the shell which are found (though often reduced in
number by coalescence) in all the typical Operculata, the “ scutum ”

D

34 Guide to Crustacea.

Table-case and “ tergum ”’ forming the movable lid or ‘ operculum,” while the

No. 3.

Table-case
No. 4.

others form the outer “ wall.” In the genus Catophragmus, how-
ever, there are numerous additional plates outside those which
usually form the wall. These outer plates correspond to the
additional capitular plates found, among the Pedunculata, in Polli-
cipes, of which a specimen is placed alongside for comparison.

One of the commonest British Barnacles is the little Balanus
balanoides which is familiar at the seaside, coating rocks and
stones as if with “rough cast.” At the other extreme of size is
another species of the same genus, Balanus psittacus, the largest
member of the sub-class, of which some fine specimens are
exhibited in Wall-case No. 4. It is found on the coasts of Chile,
where it is ‘universally esteemed as a delicious article of
food.”

Several species of sessile Barnacles are commonly found
attached to large marine animals such as whales and turtles. The
curious Tubicinella which burrows into the skin of whales is
exhibited here, and a large cluster of Coronula diadema, growing
on the skin of a whale, is mounted at the side of the doorway at
the south end of the gallery. .

Darwin’s Monograph of the Cirripedia, published 1851-1854, is
still the chief work of reference on this group of animals; it is of
special interest to the historian of biological theory, because, in the
course of its preparation, Darwin had to deal with the problems of
specific and individual variation as they present themselves to the
systematic zoologist. Like other groups of sedentary organisms,
plants and corals for example, the Cirripedia are particularly sub-
ject to great variation dependent on differences of environment, and
Darwin often found considerable difficulty in deciding as to the
limits of species. In Table-case No. 4 is exhibited a small series
of specimens selected by Darwin himself to illustrate the variations
of Balanus amphitrite, and accompanied by a list in his hand-
writing. Of this species Darwin wrote in his Monograph :—

“In order to show that it has not been from indolence that I
have put so many forms together, I may state that I had already
named and fully described in detail eight of the following forms as
species, when I became finally convinced that they were only
varieties. . . . After studying such varying forms as B. tintin-
nabulum and amphitrite it is difficult to avoid, in utter despair,
doubting whether there be such a thing as a distinct species, or at

least more than half a dozen distinct species in the whole genus
Balanus.”

Cerripedia. 35

Order 2.—Rhizocephala.

The Rhizocephala are parasites living on other Crustacea, and
they offer one of the most striking examples of the degradation in
structure associated with the parasitic habit of life. In the adult
they lose every trace, not only of Crustacean, but even of Arthro-
podous structure, although the very close resemblance of their
larval stages to those of the normal Cirripedes shows that they
have been derived from forms similar to the latter. The body is
enclosed in a fleshy mantle, which has a small opening to the
exterior. From the short stalk by which the animal is attached,

Fia. 14.

Sacculina carcimi attached under the abdomen of a common Shore-crab.
[Table-case No. 4.]

fine root-like filaments branch in all directions throughout the
body of the host (generally a Crab), and serve for the absorption
of nourishment. The parasite has no mouth or food-canal, no
limbs, and only a feebly developed nervous system.

Sacculina carcim, of which a specimen is exhibited (Fig. 14),
is found on the common shore-crab (Carcinus maenas) and other
Crabs.

The remarkable changes which the presence of Sacculina
induces in its hosts are illustrated by a series of specimens in
Wall-case No. 2 already referred to.

In their larval development the Rhizocephala pass through
Nauplius and Cypris stages closely similar to those of ordinary
barnacles. Drawings of the larval stages of Sacculina are exhibited.

D 2

Table-case
No. 4.

Table-
cases
Nos. 5-16.

Table-case
No. 5.

36 Guide to Crustacea.

Sub-class V..-MALACOSTRACA.

The body consists of nineteen limb-bearing somites (or twenty,
if the eye-stalks be reckoned as appendages). A thorax of eight
and an abdomen usually of six somites are sharply distinguished
by the character of the appendages.

This sub-class is much larger and more varied than any of the
others. It may be divided into two series as follows :—

Series 1. Leprostraca (Abdomen of seven somites).

Division 1. Phyllocarida.
Series 2. Humanacostraca (Abdomen of six somites).
Division 2. Syncarida.

A 3. Peracarida
be 4. Hoplocarida.
ee 5. Hucarida.

ae
SK \A hi
a \C NS

Y \ ~~
if RY
i
a’.
Nebalia bipes, female, from the side (enlarged). a.’, Antennule; a.”, antenna ;

ab.'—ab.°, the abdominal limbs ; ad., the deci. muscle joining the two
valves of the shell; f., the caudal fork ; ; p., palp of maxillula; 7., rostral
plate; ¢., telson; 1-7, the seven somites of the abdomen. (From
Lankester’s “‘ Treatise on Zoology,” after Claus.)

Division 1.-PHYLLOCARIDA.

The carapace is bivalved, enveloping but not coalescing with
the thoracic somites, and bearing in front a movably articulated
rostral plate. The eyes are stalked. The last somite of the abdomen
has no limbs, but the telson carries a pair of appendages forming the
“caudal fork.” The thoracic limbs are flattened and leaf-like.

The existing species belonging to this division are few in
number but are very widely distributed in all seas. Nebalva bipes,

Matlacostraca—Phyllocarida, Syncarida. 37

of which a specimen is exhibited, occurs on the British coasts and Table-case
ranges from Greenland to Chile and Japan. A coloured drawing N° ?
of a living Nebalia is hung in Wall-case No. 4.
It is probable that the fossil forms known as the Ceratiocaridae,
which are abundant in many rocks of Palaeozoic age, should be
referred to this division.

Division 2.._-SYNCARIDA.

There is no carapace, and all the thoracic somites (except, some-
times, the first) are distinct. The eyes may be stalked or sessile. The
thoracic limbs carry exopodites and a double series of plate-like gills.

, Vill

Fia. 16.

Anaspides tasmaniae, male, from the side (slightly enlarged). c.gr., “ Cervical
groove” marking off the first thoracic somite; ii-viii, the remaining
thoracic somites; 1-6, the abdominal somites. [Table-case No. 5.]

Fra. 17.

Praeanaspides praecursor, from the Coal Measures of Derbyshire,

38 Guide to Crustacea.

Table-case This division includes, among living Crustacea, a small number
No. 5. of very peculiar forms recently discovered in the fresh waters of

Tasmania and Victoria (Fig. 16). They are of special interest on
account of the fact that they appear to be survivors of an ancient
group of Crustacea of which the remains are found fossil in Car-
boniferous and Permian rocks. The drawing of the fossil Prae-
anaspides praecursor (Fig. 17), exhibited in the case, shows the
great resemblance in general form between that species and the
recent Anaspides (Fig. 16).

Division 3.—PERACARIDA.

The carapace, when present, does not coalesce dorsally with
more than four of the thoracic somites. The eggs and young are

Mysis relicta, female, from the side. c.s., ‘“ Cervical groove”; m., Brood-
pouch. (From Lankester’s ‘“‘ Treatise on Zoology,” after Sars.)

carried in a brood-pouch formed by overlapping plates attached to
the bases of the thoracic limbs.
The following Orders are included in this division :—
Order 1. Mysidacea.
,, 2. Cumacea.

Tanadacea.
Tsopoda.
Amphipoda.

Co

e

i

Or

Order 1.—Mysidacea.

The general form is shrimp-like (Fig. 18). A carapace is
present, but it leaves free at least five of the thoracic somites.

Peracarida—Mysidacea, Cumacea. 39

The eyes, when present, are stalked and movable. There are Table-case

swimming branches (exopodites) on the thoracic legs. Neo:
Most of the Mysidacea live in the sea and many species are

found on the British coasts. Macromysis flexuosus is one of the

commonest species. A coloured drawing of the closely allied

Leptomysis is hung in Wall-case No. 5. A drawing of Arachno-

mysis leuckarte in the Table-case gives an example of the remark-

able forms assumed by some deep-sea members of the Order. The

family Lophogastridae, all of which are inhabitants of the deep

sea, reach a much greater size than do the members of the other

families. A specimen of Gnathophausia calcarata from the

“ Challenger” expedition is exhibited, and alongside of it is placed

Fig. 19.

Gnathophausia willemoesvi, female, from the side, one-half natural size.
gr., & groove dividing the last abdominal somite. (From Lankester’s
“Treatise on Zoology,” after Sars.)

a copy of a coloured drawing from a living specimen of G. wil-
lemoesw (Fig. 19), showing the vivid red coloration characteristic
of many deep-sea Crustacea.

Order 2.—Cumacea.

A carapace is present, but it leaves four or five of the pos-
terior thoracic somites free. The eyes are not stalked, and are
usually coalesced into one. Swimming branches (exopodites) are
usually present on some of the thoracic limbs. The abdomen is
generally very slender, and the last pair of appendages (uropods)
are elongated. The other abdominal appendages are absent, at
least in the female.

The Cumacea are all marine, burrowing in sand and mud, and
being occasionally taken in great numbers swimming at the
surface of inshore waters. As a rule, they are very small, the
specimens of the common British species [phinoé trispinosa here

40 Guide to Crustacea.

Table-case shown being perhaps larger than the average, but in Arctic seas,

No.5. where they are especially abundant, they often attain a much
greater size, as is shown by the specimen of Duastylis goodsiri

(Fig. 20) from the Kara Sea.

ae
Fia. 20.

Diastylis goodsiri, female, from the side, enlarged. a.’, antennule; /.'—/.°, the
five pairs of walking-legs; m., brood-pouch; ps., ‘‘ pseudo-rostrum,”
formed by lateral plates of the carapace; ¢.. telson; wr., uropods. (From
Lankester’s ‘“‘ Treatise on Zoology,” after Sars.)

Order 3.—Tanaidacea.
Table-case Six of the thoracic somites are always distinct, the reduced
No. 6.

carapace involving only the first and second (Fig. 21). On each
side the overhanging carapace encloses a cayity within which les

Fira. 21.

Apseudes spinosus, female, from the side, enlarged. ea., vestiges of exopodites
on second and third thoracic limbs; oc., the small and immovable eye-
stalks; sc., scale or exopodite of antenna; w., uropod. (From Lankester’s
“Treatise on Zoology,’’ after Sars.)

(as in the Cumacea) a branchial appendage attached to the first
thoracic limb. The second thoracic limb is chelate or pincer-like,
and the second and third may carry minute vestiges of swimming-
branches (exopodites) (Fig. 21, ev.). The eyes, when present, are
set on small and immovable stalks (Fig. 21, oc.).

Peracarida-—Tanaidacea, [sopoda. 4

The Tanaidacea, which are all marine, and generally of very Table-case
small size, are of great interest as preserving, along with the No6:
Cumacea, links of connection between the stalk-eyed or “ pod-
ophthalmate” type of the Mysidacea and the sessile-eyed or
“ edriophthalmate ’’ Isopoda and Amphipoda.

Order 4.—Isopoda.

There is no distinct carapace. As a rule, only the first
thoracic somite is fused with the head, and the other seven are

imines, 2Wr

Bathynomus giganteus, about one-half natural size. (From Lankester’s
“Treatise on Zoology,” after Milme-Edwards and Bouvier.) {'Table-case
No. 6. |

free. There are no exopodites on the thoracic limbs. The eyes,
when present, are sessile. The body is usually flattened from
above downwards. The abdominal appendages are lamellar and
respiratory.

Table-case
No. 6.

42 Guide to Crustacea.

This is a very large and varied group, comprising numerous
families which are grouped under six Sub-orders.

In the Sub-order AseLuora the uropods are slender; the basal
segments of the legs are not coalesced with the body as in most
other Isopoda; the first pair of abdominal limbs are generally
fused, in the female, to form an operculum, or cover for the
remaining pairs. This group includes Asellus aquaticus, which is
common everywhere in ponds and ditches in this country, and a
very large number of marine species, mostly of small size.

The Sub-order PHREATOICIDEA includes a small number of very
peculiar species found in fresh water in Australia and New
Zealand. In these the body is flattened from
side to side, and the animals in other respects
have a superficial resemblance to Amphipoda.

In the Sub-order FLABELLIFERA the ter-
minal limbs of the abdomen (uropods) are
spread out in a fan-like manner on each side
of the telson. Many species of this group,
belonging to the family Cymothoidae, are
blood-sucking parasites of fish, and some of
them are remarkable for bemg hermaphrodite
(like the Cirripedia), each animal being at first
a male and afterwards a female. This family
includes the giant of the Order, the deep-sea

Fie. 93. Bathynomus giganteus (Fig. 22), which some-
a: times reaches an even greater size than the
Limnoria lignorum, . EG
much enlarged. | Specimen exhibited.
(After Sars.) A contrast in point of size is provided by
(Table-case No. 6.) the minute Limnoria lignorum (Fig. 23), belong-
ing to the family Sphaeromidae, which,
however, forces itself upon human attention by reason of its
destructive powers. In company with a member of the next Order,
the Amphipod Chelura terebrans, it burrows in submarine timber,
and by their enormous numbers the two species often destroy
the piles of jetties and such-like structures to an extent which is
only paralleled by the havoe wrought on land by the ‘“ White
ants’ of tropical countries. A good example of the results of
their activity is given by a piece of timber from Ryde pier
exhibited in Wall-Case No. 4 (Fig. 24). ;

The Sub-order VAnyirera is characterised by the fact that the
uropods form a pair of plate-like “valves” closing over the
remaining five pairs of abdominal appendages. This Sub-order

Peracarida—Tsopoda. 43

includes the species of Jdotea common on the British coasts, one Table-case
of which is shown in a coloured drawing hung in Wall-case No. 6, N° ©
The family Arcturidae are remarkable for the long and _ sub-
cylindrical body, very unlike that of the ordinary Isopods, and
also for the great size of the antennae, on which the young cluster
as in the specimen of Arcturus baffini (Fig. 25) exhibited here.

The Sub-order OnIscompEA comprises the familar ‘ Woodlice ”

Hie. 24.

Piece of timber from Ryde pier, showing damage caused by Limnoria and
Chelura. {Wall-case No. 4.j

or “ Slaters ° socommon in gardens. ‘They are terrestrial animals
adapted for breathing air, and sometimes having, in the abdominal
limbs, tufted air-tubes like the ‘“ tracheae”’ of insects, which serve
as respiratory organs. The terminal limbs of the abdomen are
slender or minute, and the antennules are always small. The
large “ Sea-slater,” Ligia oceanica, which is always found near the
sea and sometimes actually 7m rock pools, is intermediate in many
points of structure, as it is in habits, between the exclusively

Table-case
No. 6.

44 Guide to Crustacea.

Diver, Ds.

Arcturus baffini, female, carrying a cluster of young ones on its antennae,

(Table-case No. 6.]

terrestrial species and their marine relatives. Porcellio scaber
(Fig. 26) is one of the very common garden species.

The Isopods belonging to the Sub-order EprcaripEa are all
parasitic on other Crustacea, and their structure presents, in the

Hig. 26.

Porcellio scaber, female,
dorsal view, enlarged.
(From Lankester’s
“Treatise on Zoology,”
after Sars.)

adult state, a great variety of modifica-
tions. The two sexes are often very dis-
similar in size and shape, and some
species are hermaphrodite. A specimen
of the common Prawn (Leander serratus)
is exhibited which has, on one side of
the carapace, a swelling due to the pre-
sence in the gill-chamber of the parasite
Bopyrus squllarum. The female of the
parasite, taken out of the gill-chamber, is
shown alongside. The male, in this
Species, 1s almost microscopic in size, and
is commonly found clinging to the under
side of the female.

A still more remarkable form is shown
in the drawines of Portunion maenadis,
ua parasite of the common Shore-crab,

Carcinus maenas. The figure on the right

Peracarida—A mphipoda. 45

shows the parasite a situ in the shell of the crab. The yellow Table-case
mass is the greatly developed brood-pouch, which is distended No.6:
with eggs. The figure on the left represents a younger specimen

removed from the crab and further enlarged. The flaps of the

empty brood-pouch have been turned back.

Order 5.—Amphipoda.

As regards the segmentation of the body, the sessile eyes, and Table-case
: z : Oy ile
some other characters, the members of this Order agree with the

Gammarus locusta, male, from the side, enlarged. a’, antennule; a’, antenna;
acc, accessory (inner) flagellum of antennule; br, gill-plate; cv, coxal
plate (the expanded first segment of the leg; gn, the two pairs of ‘ gnatho-
pods”’ (prehensile legs) ; plp’”’, abdominal appendage of third pair; prp’,
prp”, first and second peraeopods or walking-legs; ¢, telson; 27, uropod ;
II., VIII., second and eighth thoracic somites; 1, 6, first and sixth
abdomina lsomites. (From Lankester’s “ Treatise on Zoology,” after Sars.)

Isopoda, but the body is usually compressed from side to side, the
abdominal appendages are not respiratory, and there are gill-
plates attached on the inner side of the bases of some of the
thoracic limbs.

The Amphipoda are grouped under three Sub-orders.

In the Sub-order GAMMARIDEA are included the typical Amphi-
poda, in which the body is more or less stout, the abdomen well
developed, and the eyes generally small. The most familiar
members of this Sub-order are perhaps the Sandhopper, Talitrus
saltator, and the Shorehopper, Orchestia gammarellus. These two

Table-case
No. 7.

AG Guide to Crustacea.

species are exceedingly common all round our coasts. They are
almost terrestrial in their habits, burrowing in the sand above
high-water mark, and sometimes at a little distance from the sea.
The two are often found together, and it is perhaps incorrect to
imply that they are distinguished in popular speech, but Talrtrus
is stated to be more common on sandy beaches, while Orchestia
is often found among rocks.

More typical representatives of the Gammaridea, however, are

Fi1a. 28.

Aegina spinosissima, one of the Caprellidae, slightly reduced.
'Table-case No. 7.}

the numerous species of Ganumarus, of which some live in the sea
and others, like the very common Gammarus pulex of this country,
in fresh water. Specimens and a drawing of Gammarus locusta
(Fig. 27) are shown in this case and a coloured drawing of the
same species, from life, is hung in Wall-case No. 6.

Of the other Gammaridea exhibited, it need only be said that
some, like Hurythenes gryllus and Stegocephalus ampulla, show
the large size reached by some species in Arctic Seas, where they
swarm in extraordinary profusion; that Acanthogammarus god-
lewskiv is one of a host of remarkable species, all closely related

WGA oplocarida—Stomatopoda. A7

to the common Gammarus, found in Lake Baikal; and that the Table-case
little Chelura terebrans is, of all Amphipoda, perhaps the most Noa:
directly important to man on account of its destructiveness to

marine timber referred to above (p. 42).

The members of the Sub-order HyprripeEa can generally be
recognised by the very large eyes, which may cover almost the
whole surface of the head. The first thoracic hmbs (maxillipeds)
are reduced. Most of the species are pelagic in habit, living at the
surface of the open sea. One of the most remarkable is Phronima
sedentaria which lives on various pelagic organisms, like jelly-
fishes and salps, and often carries about with it as a kind of cloak
the remains of its prey. One of the two specimens here shown is
enclosed in a barrel-shaped case, the remains of a swimming-bell
of one of the Siphonophoran jelly-fishes.

In the Sub-order CaprELLIDEA the body is either slender and
thread-like (Caprellidae), or broad and flattened (Cyamidae). The
abdomen and its limbs are vestigial.

The Caprellidae (Fig. 28) are generally found among Zoophytes
or seaweeds. A group of specimens mounted in natural sur-
roundings is shown in Wall-case No. 4.

The Cyamidae, or ‘‘ Whale-Lice,” are parasitic on Whales, and
are sometimes found in large numbers clinging to their skin.

Division 4.—HOPLOCARIDA.

Four or five of the posterior thoracic somites are free Table-case

from the carapace. There is no brood-pouch. ‘Two movable STOEL
segments are separated from the anterior part of the head,
bearing respectively the pedunculate eyes and the antennules,
and there is a moyable rostral plate in front of the carapace.
The first five pairs of thoracic limbs are subchelate, and the
second pair are very large. The last three pairs carry exopodites.
There are tufted gills borne by the first five pairs of abdominal
appendages.

This division includes the single order Sromaropopa, the
members of which are abundant in the warmer seas. They are
generally easily recognised by the characteristic form of the large
claws, which are not pincer-shaped, like those of Lobsters and
Crabs, but have the last segment shutting down, like a knife-blade,
on the segment before it.

One species of Squilla (S. desmarestii) occurs occasionally

48 Guide to Crustacea.

Table-case on the South Coast of England, and the much larger S.
No. 8. mantis (Fig. 29), of which specimens are exhibited from
the Mediterranean, has been found, very rarely, off the
coast of Cornwall. Both species are used for food in Mediter-
ranean countries.

The Stomatopoda have a prolonged larval development, in the

Hig. 29)

Squilla mantis, about one-half natural size. {Table-case No. 8.]

course of which the larvae assume very striking forms, and often
attain a large size. They were formerly supposed to be inde-
pendent species of Crustacea, and received the generic names of
Hrichthus, Alima, ete. The “species” Lysioerichthus edwardsiu,
of which a specimen is exhibited, has been found to be the larval
state of Lysiosquilla glabriuscula.

Eucarida—Euphausiacea. 49

Division 5.—_EUCARIDA.

The carapace is coalesced dorsally with all the somites of the Table-case
thorax. There is no brood-pouch. No. 8.
Two Orders of very unequal size are included in this Division :—

Order 1.—Huphausvacea.
» 2—Decapoda.

Order 1.—Euphausiacea.

The members of this Order were formerly included with the
Mysidacea in the Order “ Scuizopopa.” They are, however, very
closely allied to the Decapoda, and are distinguished from the

Ere. 30.

Meganyctiphanes norvegica, male, from the side, about twice natural size.
(From Lankester’s ‘* Treatise on Zoology.”’)

more primitive types of that Order chiefly by the fact that they
possess only a single series of gills (podobranchiae), and that none
of the thoracic limbs are distinctly modified as maxillipeds.

Most of these animals, like some of the lower Decapods, are
phosphorescent. The light-producing organs, situated on various
parts of the body and limbs, were formerly described as “ acces-
sory eyes’; they are seen as little red spots along the sides of the
body in the coloured drawing of Nematoscelis microps exhibited in
this case.

Meganyctiphanes norvegica (Fig. 30), one of the larger species
of the Order, occurs in deep water off the British coast. In Loch
Fyne, where the specimens here exhibited were obtained, the
species forms an important food of the herring.

50 Guide to Crustacea.

Order 2.—Decapoda.

Table- The gills are arranged typically in three series—podobranchiae,

Fo 1g, arthrobranchiae, and pleurobranchiae. Only in the aberrant genus

Leucifer are the gills entirely absent. The first three pairs of

thoracic limbs are more or less completely modified to act as jaws
(maxillipeds), while the last five form the legs.

This very extensive and varied Order includes all the larger

and more familiar Crustacea, such as Crabs, Lobsters, Crayfish,

Bie. Sie

Penaeus caramote, from the side, about half natural size.
Table-case No. 9. }

Prawns, and Shrimps. From their greater size and more general
interest, it is both possible and desirable to exhibit a much larger
series than in the other groups of Crustacea, and in Table-cases
Nos. 9 to 16 will be found representatives of all the Tribes and of
the more important families composing the Order. On the system
of classification adopted here, these tribes are wrouped under three
Sub-orders :
Sub-order 1.—Macrura.
2.—Anomura.

3,—Brachyura.

Leucarida— Decapoda. 5|

SuB-orDER I.—MACRURA.

The Macrura are generally distinguished by the large size of
the abdomen, which is symmetrical and not folded under the body.
The front, or rostrum, is not united with the “epistome.” The
sixth pair of abdominal appendages (uropods) are always
present, generally broad and flattened, forming with the telson,
a “ Tail-fan.”

The first Tribe of the Macrura, the PeNArrpera, consists of
prawn-like animals having the first three pairs of legs usually
chelate or pincer-like, and not differing greatly in size. The side-
plates of the second abdominal somite do not overlap those of the
first. Members of this Tribe are the commonest Prawns in tropical
seas, and often reach a great size. Penacus caramote (Fig. 31) is
highly esteemed for the table in Mediterranean countries, and
‘many other species are used for food in various parts of the
world. P. caramote is stated to have occurred on the Welsh
coast. Leucifer, a delicate, transparent, pelagic form, belong-
ing to this tribe, differs from all other Decapoda in having no
gills.

The small Tribe of the SreNoprpEa includes a few forms which
resemble the Penaeidea and the Astacidea in having the first three
pairs of legs chelate, but differ from them, among other characters,
in the fact that the third pair is much the largest. Stenopus, a
common tropical genus, is remarkable for the brilliant colora-
tion of the living animals. The specimen of S. hispidus ex-
hibited here has been painted so as to convey some impression
of this.

The Tribe Cartpra includes the true Prawns and Shrimps.
The first two pairs of legs are generally chelate or pincer-like, and
the first is seldom larger than the second. The second somite of
the abdomen has the side-plates broadened, so as to overlap those
of the somites in front and behind.

Only a few of the numerous families composing this tribe are
illustrated by the specimens exhibited.

The members of the family Acanthephyridae are deep-sea
animals, and possess many primitive characters. Like some of
the related families, they have swimming branches (exopodites) on
the legs. Some of them are phosphorescent.

The Nematocarcinidae are also inhabitants of the deep sea, and
are remarkable for the extreme length and slenderness of the legs,

E 2

Table-
cases
Nos. 1-16.

Table-case
No. 9.

52 Guide to Crustacea.

Table-case well shown by the specimen of N. wndulatipes (Fig. 32) from the

No. 9.

Challenger Expedition, which is exhibited here.

The Pandalidae have the first pair of legs slender and ending
in pincers so minute that, to the naked eye, the limbs appear
simply pointed. The second legs have the carpus, or “ wrist,”
divided into small segments. To this family belong the British
Pandalus montagui (the “ Pink Shrimp” of the fishmonger) and

HIG. 32.

Nematocarcirus wndulatipes. (Table-case No. 9.

the much larger P. borealis. The latter inhabits the deeper waters
of some of the Norwegian fjords, ranging from 60 to 400 fathoms
depth. In recent years, as a direct result of investigations carried
out by the zoologists of the Norwegian Fishery Department, an
important fishery of this species has been established, and large
quantities are now exported from Norway to the English and
other markets.

In the family -l/pheidae the pincers of the first pair of legs are

Decapoda —Macrura, 53

usually greatly enlarged and very dissimilar in shape. The second
legs are slender, and have the carpus, or “ wrist,” divided into
many small segments. The members of this family are very
abundant in tropical seas, especially on coral reefs. Some of them
produce a clicking noise by snapping the fingers of one of the
chelae.

In the family Palaemonidae the first two pairs of legs end in
chelae, or pincers; the second pair is larger than the first, and
has the carpus, or “ wrist,’ undivided. The antennules bear each
three terminal filaments. To this family belong the common
marine ‘ Prawns” of British coasts and the “ River-Prawns ” that
are abundant everywhere in fresh waters within the tropics. The
great size reached by some of the latter is shown by the specimens
of Palaemon carcinus from the East Indies and P. jamaicensis from

law; BB

The common Prawn, Leander serratus, slightly reduced. {'Table-case No. 9. |

the West Indies. Attention may also be directed to a specimen
of the common Prawn (Leander serratus) (Fig. 33) prepared by a
special process so as to retain the translucency of the living animal.

In the family Crangonidae the pincers of the first pau of legs
are imperfectly formed (sub-chelate) and much stronger than
those of the second pair, which are very slender. The rostrum
is usually short and flattened. To this family belong the common
Shrimp (Crangon vulgaris) and the large Arctic Shrimp (Sclero-
crangon boreas).

The Tribe AstactpEa (or NEPHROPSIDEA) includes the true
Lobsters and Crayfishes. They may be recognised by having the
first three pairs of legs chelate or pincer-like, and the first pair
very large.

The Lobsters constitute the family Homaridae, all the members
of which inhabit the sea. The last thoracic sternite is firmly fixed

Table-case
No. 9.

Table-case
No. 10.

Table-ca se

No. 10.

54 Guide to Crustacea.

to the preceding, and the male has sexual appendages on the
abdomen.

The common Lobster of Europe, Homarus gammarus, is repre-
sented on the American coasts of the North Atlantic by a closely
allied species, H. americanus. A third species, H. capensis, 18

The ‘ Norway Lobster,” Nephrops norvegicus, about one-third natural size.
fTable-case No. 10.

found at the Cape of Good Hope, but it is of small size and of no

economic importance. <A series of specimens and drawings in
Wall-cases Nos. 1 to 3, illustrating the structure and life-history
of the Common Lobster, have already been described. — The

“Norway Lobster,” Nephrops norvegicus (Fig. 34), 1s found
abundantly in certain localities in deeper water than that frequented
by the Common Lobster. It is generally sold in London shops

Decapoda— Macrura. a)

under the name of * Dublin Prawn,” although the chief supplies
now come from Scotland and the North-Hast of England, not, as
formerly, from the Irish Sea. In connection with the name
“Norway Lobster” used for this species, it should be remembered
that the common Lobster is abundant on the coasts of Norway,
and that large quantities are exported thence to England.

In the true Crayfishes, which belong to two families inhabiting
respectively the fresh waters of the Northern and Southern Hemi-

tive, Bis),

Astacopsis franklinii, about 4th natural size. [Wall-case No. 5.

spheres, the last thoracic sternite is movable. In the Northern
Crayfishes, belonging to the family Astacidac, the male has sexual
appendages on the abdomen.

The largest of the Crayfishes found in Western Europe, and
the most highly esteemed for food, is the ‘‘ Red-clawed Crayfish,”
Astacus fluviatilis (French, “ Kerevisse & pattes rouges,”’ German,
“ Edelkrebs’’), found in France, Germany, Austria, N.W. Russia,
S. Sweden, Denmark, &e. Although the name dA. fluviatilis is
sometimes applied to the English Crayfish, it 1s more correctly
restricted to the Red-clawed species, which does not occur in the
3ritish Islands.

Table-case

No. 10.

Table-case

No. 10.

Table-case
No. 11.

56 Guide to Crustacea.

The ‘ White-clawed Crayfish,” Astacus pallipes (French,
“ Berevisse a pattes blanches,’ German, ‘ Steinkrebs”’), is found
in England and Ireland, France, South Germany, Italy, &c. It is
little used for food, being regarded as much inferior to A. fluviatilis.

Astacus leptodactylus is a large species found in the Lower
Danube and its tributaries, and in Russia, especially in those rivers
that flow into the Black Sea and the Caspian. It is occasionally
used for the table, but is regarded as inferior in quality.

In North America, east of the Rocky Mountains, numerous
species of crayfish of the genus Cambarus are found. A few of
these live in the subterranean waters of caves, and, like many
other subterranean animals, are blind. The best known species is
Cambarus pellucidus, from the Mammoth Cave in Kentucky, of
which a specimen is exhibited.

In the Southern Crayfishes, forming the family Parastacidace,
there are no sexual appendages in the male. Numerous species
of this family occur in Australia, and Astacopsis spinifera, known
as the “ Murray River Lobster,” is used for food. Like the closely
alhed A. franklini (Fig. 35) of Tasmania (of which a specimen is
exhibited in Wall-case No. 5), it sometimes grows to a great size.
The occurrence of Astacoides madagascariensis on the island of
Madagascar is remarkable, since no Crayfishes are found anywhere
on the African continent.

The members of the tribe Loricara (or ScYLLARIDEA) are
large, lobster-like Crustacea. They may be distinguished from the
true lobsters by having no chelae (the last pair of legs only are
imperfectly chelate in the female). In the family Palinuridae the
body is more or less cylindrical, and the antennae are long,
cylindrical and jointed, while in the Scyllaridae the body is more
or less flattened, and the antennae are expanded into broad plates,
which are said to be used as shovels in burrowing. To the former
family belongs the Spiny Lobster or Sea Crawfish (French,
‘“ Langouste”’), Palinurus vulgaris (Fig. 36), which is found on the
Southern and Western coasts of the British Islands, and of which
two large specimens are mounted in Wall-case No. 6. Numerous
species of Spiny Lobsters occur in the warmer seas, and they are
used for food in many parts of the world. The brilliant colouring
of many tropical species is illustrated by a specimen of Panulirus
ornatus coloured as in life. The only species of the Scyllaridae
found in British waters is Scyllarus arctus (Arctus wrsus) of which
a Mediterranean specimen is exhibited. It occurs, rarely, off the
south-western coasts of England.

Decapoda—NMacrura.

The common Spiny Lobster, Palinurus vulgaris, much reduced.
[Wall-case No. 6.]

Table-case
No. 11.

58 Guide to Crustacea.

The larvae of the Loricata are very unlike those of the related
groups, and are remarkable for their extremely flattened form and
glassy transparency, and for the large size which they sometimes
attain. They were formerly regarded as adult and independent
species of Crustacea, and received the generic name _ of
Phyilosoma (Fig. 37).

Representatives of the extinct family Glyphaeidae are found
fossil in rocks of Mesozoie age, from the Trias onwards. In some

Ai \N

. co
we SH
SSS
= Si
7 jee

hie, By

The “ Phyllosoma” larva of the common Spiny Lobster, much enlarged.
(After J. T. Cunningham.)

characters, such as the possession of a scale or exopodite on the
antenna, and sometimes in having true chelae, they are much
more primitive than the existing Loricata. A drawing of Glyphaea
regleyana trom the Jurassic of France is exhibited.

In the Tribe EryonrpEa the first four, and sometimes all five,
pairs of legs are provided with chelae. Special interest attaches to
this tribe on account of its geological antiquity. Fossil forms, not
very different from those now living, are found in rocks of
Mesozoic age, from the Trias onward.

Decapoda—Macrura, Anomura. 59

The existing species are confined to the deep sea, and, like Table-case
CP

many other deep sea animals, are blind.

Some, at least, are No. 11.

phosphorescent, and a living example of Polycheles phosphorus (of
which a specimen is exhibited) (Fig. 38) was observed by Dr. Alcock

to be “luminous at two points
between the last pair of thoracic
legs where there is a_ triangular
glandular patch.’ A copy of a
drawing made from a living speci-
men of another species, Polycheles
sculptus, dredged at a depth of 695
fathoms in the Gulf of Panama,
shows the red coloration that is very
characteristic of deep-sea Crustacea.

The fossil species are represented
by a cast of Hryon arctiformis, from
the Lithographic limestone (Jurassic)
of Solenhofen in Bavaria.

The members of the tribe THa-
LASSINIDEA are burrowing forms,
with a soft, loosely built body. They
form, in some respects, a transition
to the Anomura, in which, in some
systems of classification, they are
included.

In the genus Callianassa, of
which one species, C. suwbterranea,
occurs on the south coast of England,
one of the chelae of the first pair of
legs is much larger than the other
and is of peculiar form. A specimen
of the large C. armata from the
Fiji Islands is exhibited.

Thalassina anomala is a widely
distributed tropical species, especially
characteristic of mangrove swamps,

Fig. 38.

Polycheles phosphorus, female.
(After Alcock.) [Table-case
No. 11.]

but sometimes found burrowing in damp earth at a consider-

able distance from the sea.

Sus-OrpER 2.—ANOMURA.

The Anomura commonly have the abdomen more or less bent Table-case

under the body, or else spirally coiled and asymmetrical.

The No. 12.

60 Guide to Crustacea.

Table-case front, or rostrum, is not united with the epistome. The sixth pair

No. 12.

of abdominal appendages (uropods) are rarely absent. The last pair
of legs are reduced in size and the last thoracic sternum is movable.

The Sub-order is divided into three tribes, of which the first,
PAGURIDEA, includes the Hermit-Crabs and their allies. With few
exceptions, the most important of which are the Coco-nut Crab,
Birgus, and the family Lithodidae, the members of this tribe have
the abdomen soft, not distinetly segmented, and spirally twisted in

Fie. 39.

The common Hermit-Crab, Hupagurus bernhardus, in the shell of a
whelk, reduced. |Table-case No. 12. |

adaptation to the habit of living in the empty shells of Gasteropod
Molluses.

The marine Hermit-crabs, forming the family Paguridae, nearly
all live in shells, :and very often the outside of the shell gives
attachment to Sponges, Hydroid Zoophytes, or Sea Anemones,
between which and the Hermit there may exist more or less definite
relations of ‘‘commensalism.” In the case of Paguropsis typica,
here exhibited, no shell is carried, but the abdomen is protected by
a cloak of living sea anemones held in position by the hinder
legs of the crab. The commonest British species, Hupagurus
bernhardus (Fig. 39), and one of the largest representatives

Decapoda—A nomura. 61

of the family, Pagurus punctulatus, are also placed in this Table-case

case. No. 12.
The members of the family Coenobitidae ave Land-crabs,

though their early stages are passed in the sea, and the adults visit

the sea periodically. The species of Cocnobita carry shells about

with them like the marine Paguridae, but the ‘“ Robber-Crab ” or

}

\
{
\
t

Fic. 40.

The Coco-nut Crab, Birgius latvo, much reduced. [Wall-case No. 6. |

“ Coco-nut Crab,” Burgus latro (Fig. 40), of which a specimen is
shown in Wall-case No. 6, has given up the habit of carrying a
portable dwelling, and the dorsal plates of the abdomen, which in
the other hermit-crabs are soft and membranous, have again
become hard and shelly.

The stories told of the tree-climbing habits of Birgus have otten
been doubted, but the matter is set at rest by a photograph exhibited
in Wall-case No. 6. This photograph was taken on Christmas

62 Guide to Crustacea.

Table-case [sland, in the Indian Ocean, by Dr. C. W. Andrews, F.R.S., of the
Ligh ies Geological Department of the Museum, and it shows a specimen
of Birgus in the act of descending the trunk of a sago-palm.

The members of the family Lithodidae have become completely
crab-like in shape, and were formerly classified with the Brachyura,
with which, however, they have no direct affinity. They may be
at once distinguished from the true Crabs by having only three
pairs of walking-legs visible behind the chelipeds, the last pair
being carried folded up within the branchial chambers. Their
relationship to the Hermit-Crabs is shown by the fact that the

Mie. 45

The “ Northern Stone-Crab,” Lithodes maia, much reduced. The last pair of
legs are folded out of sight in the gill chambers. ['Table-case No. 12. |

abdomen is frequently asymmetrical, and has appendages only on
one side. The last pair of abdominal appendages (aropods) are
wanting.

The “ Northern Stone Crab,” Lithodes maia (Fig. 41), found on
the more northerly coasts of the British Islands, belongs to this
family. Cryptolithodes is an allied genus in which the carapace is
expanded at the sides so as to cover the limbs completely. A
specimen of the large Hchidnocerus cibarius found on the West
Coast of North America is placed in the lower part of Wall-case
No. 2.

Decapoda— A nomura. 63

In the Tribe GALATHHIDHA the body is symmetrical, and more Table-case
or less lobster-like, but the abdomen is bent upon itself, and No. 12.
sometimes folded under the ‘body. The last pair of legs are
slender and are carried folded up within the branchial chambers.
The last pair of abdominal appendages (uropods) are large,
forming a well-developed tail-fan.

Hie. 42:

Munida rugosa (reduced). {Table-case No. 12.
( ( |

Several species of Galathea occur on the British coasts, G.

strigosa being the largest. Munida rugosa (Fig. 42) is found in
rather deep water in British seas. The family Uroptychidae

ineludes only deep-sea species and is represented by the brilliantly
coloured Humunida picta. The family Aeglecdae comprises only a
single species, Aeglea laevis, which is interesting as being the only

1g

Anomuran inhabiting fresh water. It is found in South America,

64 Guide to Crustacea.

Table-case especially in mountain streams. In the family Porcellanidae, the
No. 12. short and broad carapace, without a prominent rostrum, and the
fact that the abdomen is folded under the body, give the animals
quite a crab-like appearance. They are, however, very closely
allied to the Galatheidae. All the species are found in shallow
water. The little “‘ Porcelain Crabs ” (Porcellana) of British coasts
are represented in tropical seas by numerous species, some of which,

like those exhibited, are of considerable size and striking colours.
The small tribe Hipprpra in-
cludes small, crab-like, burrowing
forms, living in sand and having
the feet flattened for digging.
They are only found in the warmer
seas. In one of the families of
this tribe, the Albuneidae (Fig. 43),
when the animals are buried in
sand, respiration is carried on by
means of a tube formed by the
long antennules, each of which
bears a double row of stiff hairs.
It is noteworthy that in the Bra-
chyuran Corystidae (see Table-case
No. 15), which have a very similar
respiratory siphon, it is formed,
not, as in this case, by the
antennules, but by the antennae.

Fia. 43.

SUB-ORDER 3.—BRACHYURA.
Albunea symnista (reduced).
Table-case No, 12. ] The BRAcHYURA, or true
Crabs, are distinguished from the
Table- other Decapoda by having the abdomen short and bent wp under
ee athe body. The “front” sends down a process to meet the
epistome, and thus forms a septum between the antennules. The
sixth pair of abdominal appendages (uropods) are generally absent,
rarely present as rudiments. The third pair of maxillipeds are
generally broad and flattened, forming a pair of ‘folding doors”
which cover the other mouth-parts.
The Brachyura are usually divided into five Tribes, which,
however, are not all of equal value :—
Tribe 1— Dromiacea. Tribe 8—Oxyrhyncha.
5 2—Oxystomata. , 4—Cyclometopa.

Tribe 5-—Catometopa.

Decapoda— Brachyura, Crabs. 65

The Dromiacna or Sponge-Crabs are the most primitive of the
existing Brachyura. The last pair, or the last two pairs, of legs are
dorsal in position, with hooked or prehensile claws, and are used
for holding a piece of sponge, an Ascidian, or half of a bivalve
shell, under which the animal is completely hidden. The mouth-
frame is square. The primitive character of the group is shown
especially by the retention of a vestigial pair of limbs on the first
abdominal somite of the female, and: often on the sixth abdominal

Dromia vulgaris. Front view of a specimen carrying on its back a mass of the
sponge Clione celata (reduced). [Table-case No. 12.

somite in both sexes (see the exhibited specimen of Dromia lator).
The basal segment of the antenna is large and unusually free,
the pits into which the antennules fold are not separated from the
orbits, and the gills are, in most cases, more numerous than in the
other Brachyura. The oviducts of the female open on the first
segment of the third pair of legs.

Many of the Dromiacea, especially the more primitive forms,
inhabit the deep sea. Dromia vulgaris (Fig. 44), which occurs off
the South of England, belongs to the family Dromiidae, in which
the last two pairs of legs are generally reduced in size, and are

F

Table-case
No. 12.

66 Guide to Crustacea.

Table-case elevated on the back. One of the specimens exhibited, taken in
No. 12. >: : : : : :
the Bristol Channel, carries as a cloak a specimen of the sponge
Clione celata. In the family Dynomenidac, represented by the
little Dynomene hispida, only the last pair of legs are reduced and
elevated on the back.
Latreillia elegans belongs to the aberrant family Latreillidae.
In the triangular shape of the carapace and the length and slender-
ness of the legs, the members of this family show a certain
similarity to the Spider Crabs of the Tribe Oxyrhyncha.
To this group also belongs the family Homolidae, a typical
example of which is the large Homola (Paromola) cuvierr (Fig. 45),

Imigel, 4!55.

Homola cuvieri. The carapace of this specimen is about seven inches long.
[ Wall-case No. 5.]

exhibited in Wall-case No. 5. This species has occurred, very
rarely, on the west coasts of Ireland and Scotland.

The members of the family Prosoponidae are only known as
fossils, but it has recently been shown that they are closely allied
to the living Dromiacea, especially to the deep-sea Homolodromidae.
They range from the lower Oolite to the Upper Cretaceous. A
cast of the carapace of Prosopon mammillatum illustrates this
family.

Table-case The members of the tribe OxystomaTa, sometimes known as
No. 13. « Sand-Crabs,” may be recognised by the triangular shape of the
mouth-frame, which is narrowed in front and extends forward
between the eyes. The channels which carry the outward stream

Decapoda—Brachyura. 67

of water from the gills, and in most other crabs open at the front Table-case
corners of the mouth-frame, are produced forwards to the front of No. 13.
the head and are closed in below by plate-like processes from the
endopodites of the first maxillipeds. This arrangement is cor-
related with the characteristic habits of the tribe, nearly all the
members of which conceal themselves in the sand, where they lie
buried with only the eyes exposed.

In the family Calappidae the openings by which the water
enters the gill-chambers are situated, as in most Brachyura, in
front of the, bases of the chelipeds. The legs are normal in
position.

A specimen of Calappa hepatica is exhibited which has been
prepared to illustrate the distinctive characters of the tribe. The
second and third maxillipeds have been removed on one side to
show the triangular mouth-frame (coloured red) and the process
from the endopodite (coloured blue) of the first maxilliped. The
arrow indicates the course of the respiratory current. A broad
space (marked X), free from hair, is seen on each side of the
mouth-frame leading down to the entrance of the gill-chamber.
When the chelipeds are closed up against the under surface of the
body, as in one of the specimens of Calappa flammea exhibited, this
space is converted into a tubular channel, through which a supply
of pure water can reach the gills when the crab is buried in the
sand.

The species of the genus Matuta swim well by means of their
flattened, paddle-shaped feet, which are also used for digging in
sand. The animals are said to bury themselves with wonderful
rapidity. The channel leading to the entrance of the gill-chamber,
seen in the preparation of Calappa, is here much deepened in its
front portion, where the overarching hairs convert it into a tubular
passage opening into the orbit.

In the family Lewcosiidae the channels leading to the gills are
completely covered in by the expanded exopodites of the third pair
of maxillipeds. This character is illustrated by a preparation of
Parilia alcocki (the largest species of the family), in which the
second and third maxillipeds have been removed on one side.
The mouth-frame is coloured red and the endopodite of the first
maxilliped blue. X marks the inhalent respiratory channel. One
of the third pair of maxillipeds is mounted separately to show the
greatly expanded exopodite which, in the natural position, covers
the inhalent channel.

The only Oxystomata found in British seas are several species
F 2

Table-case
No. 13.

Table-case
No. 14.

O68 Guide to Crustacea.

of the genus Hbalia. They are small Crabs, resembling the pebbles
among which they are found. Specimens of Hbalia tuberosa are
shown in their natural surroundings in Wall-case No. 11.

In the family Dorippidae the afferent branchial openings are
in front of the bases of the chelipeds. The abdomen is not com-
pletely concealed under the cephalothorax. The last two pairs of
legs are elevated on the dorsal surface of the body, and have the
terminal segments more or less distinctly modified to form a pre-
hensile claw. The Dorippidae appear to have given up the sand-
burrowing habits characteristic of other Oxystomata, and they
conceal themselves by holding a piece of sponge or some other
object over, the back by means of the hinder legs. Many of the
species inhabit the deep sea.

In the Raninidae the water seems to enter the branchial
chamber from behind, between the edge of the carapace and the
bases of the last pair of legs. As in Dorippidae, some of the
abdominal somites are visible from above, and the last pairs of legs
are elevated on the dorsal surface. The legs, however, are flattened
and paddle-like, and appear to be used for swimming and digging,
as in Matuta. The “frog-crab,” Ranina scabra, is, in general
appearance, one of the most striking and aberrant of the Brachyura.

In the Tribe OxyrHyNncuHa the carapace is usually triangular in
shape, narrowed in front, and produced to form a rostrum. The
mouth-frame is square. The genital ducts of the male open on
the bases of the last pair of legs. As a rule, the legs are long and
slender.

The Crabs of this tribe are generally sluggish and inactive
animals, and many of them, as already mentioned, have the habit
of masking themselves with seaweed, sponges, etc. This habit is
illustrated by some of the preparations in Wall-case No. 6, and
evidences of it will be noticed on many of the specimens in this
case.

The members of the family Mazdae are known as “ Spider-
crabs.” In these, the chelipeds are very mobile, and are usually
not much stronger than the other legs. The orbits are more or
less incomplete. Among the specimens exhibited may be men-
tioned Macropodia longirostris, 2 common British species which
has the long and slender legs that are typical in the group.
Huenia proteus is noteworthy for the leaf-like expansions of the
carapace; in life it is of an olive-green colour and is difficult to
detect among the foliaceous sea-weeds which it frequents. To
this family belongs the large Spider-crab of the South and West

Decapoda—Brachyura. 69

coasts of England, Maia squinado, a large specimen of which is Table-case
exhibited in Wall-case No. 4. No. 14,

Fie. 46.

The Giant Japanese Crab, Macrocheira kaempferi, male. The scale of the
figure is given by a two-foot rule placed below the specimen. {Specimens
of the male are mounted above Wall-cases 3 and 4, and one of the female
above Wall-cases 1 and 2.

Another noteworthy member of the family is the Giant
Japanese Crab Macrocheira (or Kaempferia) kaempfert (Fig. 46),
the largest of existing Arthropoda, of which two male specimens

Table-case
No. 14.

Table-case
No. 15.

70 Guide to Crustacea.

and a female are mounted above the Wall-cases at the south end
of the Gallery. They were coloured after a drawing of a live
specimen by a Japanese artist.

In the family Parthenopidac, the chelipeds are usually much
more massive than the other legs, and the orbits are well
formed. The typical members of this family have taken to the
same habitat as the Oxystomata, burying themselves in sand or
shingle, and they show many superficial resemblances in the
shape of the chelipeds, the lateral extensions of the carapace, and
the disposition of the breathing channels, to such Oxystomes
as Calappa. In many species, as in the Parthenope horrida
exhibited, the carapace and limbs are remarkably rugged and
uneven.

The Crabs belonging to the Tribe CycLometora have the
carapace, as a rule, broader than long, with the antero-
lateral borders strongly curved, and _ the postero-lateral
borders convergent; the front is not produced into a_ ros-
trum; the mouth-frame is square; the genital ducts of the
male open on the bases of the last pair of legs. With the
exception of the River-crabs, all the members of this tribe inhabit
the sea.

In the large and very varied family Xanthidac, the carapace,
as arule, is transversely oval, and its surface is often lobulated.
The species of this family are very abundant, especially in the
tropics, in the littoral region. Three species of Xantho are
British, one of which, XY. <incisus, is exhibited. The vivid
colours of some tropical species are exemplified by the painted
specimens of Carpilius maculatus and Zozymus aeneus. To this
family also belongs the large Tasmanian Crab, Pseudocarcinus
gigas, % specimen of which is mounted above Wall-cases Nos. 5

and 6.

A specimen of Zozymus aeneus is exhibited which has been
prepared to illustrate the disposition of the branchial passages in
Cyclometopa, for comparison with similar preparations of the
Oxystomata in Table-case No. 15. The third maxilliped has been
removed on one side to show the quadrilateral shape of the
mouth-frame (coloured red), characteristic of most Brachyura.
The arrow indicates the course of the respiratory current, which,
however, may sometimes be temporarily reversed, especially in
burrowing species.

The typical members of the family Portunidae (Swimming
Crabs) may be recognised by the flattened, paddle-shaped, last

Decapoda—Brachyura. 71

pair of legs. Two British species of the genus Porlunus are Table-case
exhibited : the colours of P. depwrator have been carefully copied N°: 15:
from a living individual, and the specimen is mounted on a sample

of the shell-gravel on which it was actually caught. The large

Fig. 47.

Pseudocarcinus gigas, from Tasmania. The carapace of this specimen is just
over a foot in width. [Above Wall-cases Nos. 5 and 6.}

Neptunus pelagicus is the commonest edible Crab in many parts
of the Kast. The Common Shore-Crab, Carcinus maenas, is also
referred to this family, although the paddle shape of the last legs
is not so marked as in the more typical Portunidae.

Table-case
No. 15.

79 Guide to Crustacea.

Podophthalmus vigil (Fig. 48) 1s remarkable for the great length
of the eye-stalks, which is quite unusual among the Cyclometopa,
and gives this Crab a curious likeness to the genus Macroph-
thalmus among the Ocypodidae (see Table-case No. 16). The
resemblance, however, is quite superficial, for in this case it is the
first of the two segments of the eye-stalk which is elongated, while
in Macrophthalmus it is the second.

The genus Platyonychus, of which a group of specimens is
mounted in Wall-case No. 5, also belongs to this family.

The Cancridae are distinguished from the preceding families by
having the antennules folded longitudinally instead of transversely.

Fie. 48.
Podophthalmas vigil (reduced). [Table-case No. 16.

To the typical genus Cancer belongs the Edible Crab of British
coasts, of which a large specimen is exhibited in Wall-case No. 5.
The wide distribution of the genus is illustrated by species from the
Azores and from New Zealand.

The family Potamonidae, (Thelphusidae) comprises the River-
Crabs. In the shape of the carapace, which is generally more or
less square, and in having the front bent downwards, these Crabs
show some resemblance to the next Tribe, Catometopa. They are
widely distributed in fresh waters throughout the Tropics. Potamon
edule (better known as Thelphusa fluviatilis) occurs in Italy and
other parts of Southern Europe.

The family Corystidae ineludes Crabs which are allied to the
Cancridae, but have long antennae, and the third mawxillipeds are

~

ecapoda SVAChYUrea. 13
D if Ve hi

elongated, extending over the front edge of the mouth-frame. The
latter character recalls the Oxystomata, which the members of this
family also resemble in their sand-burrowing habits. Corystes
cassivelaunus (Fig. 49) is a common British species. The claws
or chelipeds are much elongated in the male. The antennae
are much longer than is usual in the Brachyura, and each bears
a double row of bristles so arranged that when the antennae are

Table-case
No. 15.

Female. Male.
Fie. 49.

Corystes cassivelawnus (slightly reduced). {Table-case No. 15.

brought together they form a tube, through which respiration can
be carried on while the animal is buried in sand.

In the tribe CaromrEropa the carapace is typically more or less
quadrate, with the front strongly bent downwards ; the mouth-
frame is square ; the genital ducts of the male open on the sternum.
A large proportion of the Crabs belonging to this tribe live on
land, in fresh water, or between tide-marks on tropical shores.
Only the chief families are illustrated in this Case.

The family Geocarcinidae (or Gecarcinidae) comprises the true

Land-Crabs, although some members of the other familes also

Table-case

No. 16.

74 Guide to Crustacea.

Table-case are almost entirely terrestrial in habits. The carapace is more or

No. 16.

less transversely oval, and the front is of moderate breadth. The
branchial regions of the carapace are generally swollen, and the
liming membrane of the gill-chamber is richly supplied with blood-
vessels, and acts as a lung. Typical genera are Geocarcinus, Car-
disoma, and Uca.

The Crabs of the family Grapsidae are the most typical Cato-
metopa. The carapace is nearly quadrilateral, with the front very
broad, and the orbits near the antero-lateral corners. Many
species are estuarine or fluviatile in habitat. The species of
Grapsus and allied genera are common shore Crabs in all the
warmer seas.

The genus Sesarma and its allies include, for the most part,
amphibious fresh-water Crabs, abundant in the tropical regions of
the Old and New Worlds.

Varuna litterata is widely distributed throughout the Indo-
Pacific region, and seems to be equally at home in fresh water and
in the sea. It is often found clinging to drift-wood at the surface
of the sea.

The little Planes minutus also lives at the surface of the open
sea, clinging to floating weed or drift-wood, or to the bodies of
large marine animals such as turtles. It is especially abundant
in the Sargasso Sea, but is widely distributed in the warmer regions
of all the oceans, and is occasionally carried to the South and West
coasts of the British Islands. It is related of this species that
‘““Columbus, finding this alive on the Sargasso floating in the sea,
conceived himself not far from some land, on the first voyage he
made on the discovery of the West Indies” (Sloane, Nat. Hist.
Jamaica, ll. p. 2).

In the family Ocypodidae the front is generally narrow and the
eye-stalks are often very long. Most of the species are amphibious
shore Crabs, burrowing and often gregarious in their habits.
Several species of the typical genus Ocypoda are exhibited.

The species of Gelasimus, often called ‘“ Fiddler Crabs” or
‘Calling Crabs,’ are common on most tropical shores, living in
vast numbers in salt marshes or between tide-marks, where they
make burrows in the sand or mud. <A group of specimens of two
species is mounted in Wall-case No. 5. The genus is of interest

-as exhibiting in an extreme degree two characters which are more

or less marked in nearly all Crabs—the unequal development of
the chelae or pincers on the two sides of the body, and their
sveater size in the male sex. The large, brightly coloured claws

Decapoda Brachyura. 75

are used by the males in fighting with each other, and are also

believed to serve to attract the females.
Gelasimus tangeri occurs on the Spanish coast near Cadiz,
where there is a regular “ fishery’? for these Crabs. Only the

large claws of the males are taken, and are prepared for the
market by cooking and then drying. After the claw has been
torn away, the Crab grows a new one in its place, but these
regenerated claws are smaller, and are regarded as of inferior quality.

Fire. 50.

Gelasimus tangeri, male (below) and female (above). [Table-case No. 16.

The genus Macrophthalmus (Fig. 51) has already been men-
tioned (p. 72) as having a superficial resemblance to the Portunid
Podophthalmus.

The members of the family Pinnotheridae are small parasitic
or commensal Crabs, living in the mantle-cavity of bivalve Mollusca,
in Aseidians or Echinoderms, or in coral-stocks. The shell is
usually soft, and the eyes, antennules, and antennae much reduced.
A preparation is exhibited of a Sea-Urchin, Strongylocentrotus
gibbosus, found on the coast of Chile. One half of the shell has
been cut away to show the Crab Pinnaxodes chilensis lying in a

Table-case

No. 16.

-

76 Guide to Crustacea.

Table-case large pouch which is formed by enlargement of the terminal part
No. 16. of the Sea-Urchin’s intestine.

The family Gonoplacidae includes Crabs that in many respects
approach the tribe Cyclometopa. The only British species is
Gonoplax rhomboides.

The small Crabs included in the family Hymenosomidae have

wire, Sul,

Macrophthalmus pectinipes, reduced. [Table-case No. 16.

a more or less triangular front, and in other respects show some
resemblance to the Oxyrhyneha. Halicarcinus planatus, of which
specimens obtained by the “ Discovery” Expedition at the Auck-
land Islands are exhibited, is found throughout the whole of the
“ Sub-Antaretic””? region, occurring at such distant poimts as the
Falkland Islands, the Cape, Kerguelen Island, and New
Zealand.

Trilobita.

“I

ae |

€lass 2:—T RIEOBITA:

The members of this class are known only in the fossil state, Table-case
and are characteristic of the strata of the Paleozoic era. They N° !7-
are especially abundant in the Silurian and pre-Silurian rocks.

On the whole, they seem to be most closely related to the
Arachnida, and especially to the Xiphosura or King-crabs, but in
certain features they resemble the Crustacea, and some authorities
are of opinion that they are allied to that class. The somites of

Bie. 52.

Reconstruction of a Trilobite, Triarthrus becki.
Natural size (after Beecher).

the body are variable in number, each, so far as is known, being
provided with a pair of appendages which, with the exception of
the pre-oral pair, are substantially similar in structure and function.

The dorsal plates of the five somites composing the anterior
region of the animal (the ‘‘ head” or prosoma) are fused to form
a carapace or “cephalic shield”; its median area is vaulted, and
each of the lateral areas is expanded, laminate, and divided by a
groove into an inner and an outer portion ; upon the latter a large
compound eye is present.

The somites of the middle portion of the body (thorax or

Table-case
No. 17.

78 Guide to Trilobtta.

mesosoma), which vary in number from two to as many as twenty-
nine, were movably jointed together in the living animal. Each
consists of a vaulted dorsal area (the tergum), and a flat mem-
branous ventral area (the sternum), and, on each side, a laminate
expansion overlapping the greater part or the whole of the legs.
The convexity of the terga and of the upper surface of the lateral
laminae gives to the body a three-lobed appearance, from which
the name Trilobita is derived. The dorsal and lateral plates of
the somites of the posterior region of the body (pygidium or
metasoma) are immovably united, although generally defined by
transverse grooves.

The appendages of the first pair, where known, are each in the
form of a single long, branched, antenniform limb. Those of the

i
y

)!

<oMUIU({ {| |

Idi Gs},

Examples of Trilobites. A—Calymene blumenbachii (Upper
Silurian). B—Ogygia buchii (Ordovician).

remaining pairs consist of two branches rising from a common
basal segment. The external branch is slender, many-jointed, and
furnished with a series of slender branchial filaments; the internal
branch, constituting the locomotor portion of the limb, consists
of six or, including the basal segment, seven segments. The post-
oral appendages of the prosoma resemble those of the rest of the
body, except that the inner extremities of the basal segments are
toothed to act as jaws.

The Trilobites are an extinct group of marine Arthropoda which
probably resembled the existing King-erabs in habits, and crept
about the bottom of the sea, feeding upon worms and other soft
animal organisms, which were crushed between the basal segments
of the anterior appendages. On account of the softness and
membranous nature of the sternal region they were able to double

Trilobita. 79

up the body or roll it up in a sphere, like wood-lice (as shown by Table-case
two of the specimens of Calymene blumenbachii in Table-case 17) ; No- 17-
and this habit, coupled with the strong spines with which the
dorsal area was frequently armed, suggests that the Trilobites
themselves were in need of protection from more powerful inhabi-
tants of the seas.

About 2,000 species have been described from Cambrian and
later beds of the Paleozoic period, at the close of which the group
became extinct.

A restoration and drawings of Triarthrus beck: and a few
specimens and casts of other Trilobites are exhibited in Table-case
17. The attention of those who are interested in these Arthropods
is directed to the account of them which appears in the “ Guide
to the Fossil Invertebrate Animals,” and to the series of speci-
mens displayed in the Geological Department (Gallery 8, Table-
case 25, Wall-case 14 b).

80 Guide to Arachnida.

Class 3.—_ARACHNIDA.

Table- The Arachnida, a class which includes such familiar animals
caaes as the spiders, scorpions, and mites, constitutes one of the main

INI@SaME EUS, 5 bs ;
divisions of the Phylum Arthropoda. The earlier members of the

class led an aquatic life, and the middle region of the body, in
these forms, was furnished with large plate-lke respiratory
appendages, suitable for breathing oxygen dissolved in water.
The King-crabs are the only surviving representatives of these
branchiferous forms. The rest of the living Arachnids are almost
invariably terrestrial forms, and the respiratory lamellae have
either sunk below the surface of the body, and become adapted to
breathe atmospheric oxygen, or have been entirely replaced by
tracheal tubes.

In the more primitive forms three principal divisions of the
body can be distinguished. The dorsal plates of the first of these
(prosoma or ‘‘ cephalothorax ”’) are fused to form a carapace, and
its appendages are six in number. The middle region of the body
(mesosoma) is nearly always fused with the posterior region
(metasoma), to form a single division (the opisthosoma or
‘“‘abdomen’’). The mesosomatic appendages may number six,
but are often suppressed or reduced in number. In its primitive
form the metasoma consists of six distinct limbless somites and
a post-anal spine or sting.

The class is composed of two divisions: 1. The Huarachnida
or Arachnida proper, which includes the Scorpions, Spiders, Mites,
etc., and also the King-crabs and the extinct forms known as
Eurypterines. 2. The Pycnogonida, or Pantopoda, a marine
croup of doubtful affinities.

TABLE OF CLASSIFICATION OF THE ARACHNIDA.

Cuass—ARACHNIDA.

Sub-class 1.—KUARACHNIDA.
Division A.—DELOBRANCHIA.
Order 1.—Xiphosura (King-crabs).
2.— Gigantostraca (Kurypterines—Fossil forms).

”

(8)
e—

Fruarachnida—xX tphosura.

Division B.—EMBOLOBRANCHIA.
Order 1.—Scorpiones (Scorpions).
», 2.—Pedipalpi (Whip-scorpions and their allies).
» 3.—Palpigradt.
,, 4.—Araneae (Spiders).
, 0—Solifugae (False Spiders).
» 6.—Pseudoscorpiones (False Scorpions).
» ¢.—Podogona.
3 8.—Opiliones (Harvest-men).
9.—Acarv (Mites).
Sub- lace 2 .—PYCNOGONIDA.

Sub-class 1—EUARACHNIDA.

Both the prosoma (‘ cephalothorax”’’) and the opisthosoma
(“abdomen ”’) are well developed in these Arachnida and are
typically separated from one another by a praegenital segment,
which generally disappears, however, in the adult. The prosoma
is usually covered dorsally by an undivided carapace which
is, however, sometimes segmented posteriorly. Its appendages
number six pairs. The first pair (‘“ chelicerae’’) are often chelate
or prehensile, whilst the second, third, and fourth pairs may also
be chelate, but are usually feelers (palps) or walking legs. When
fully developed, the mesosoma consists of six somites, which bear
plate-like appendages in the aquatic species; in the land forms
these appendages are much reduced and modified or absent.
The metasoma also typically consists of six somites, which are
devoid of appendages. The mesosoma and metasoma are often
fused to form an opisthosoma or “abdomen,” and obliteration of
segmentation often takes place.

The Euarachnida are divided into two Grades :—

Division A.—DHLOBRANCHIA.

The respiratory organs of the Delobranchia are of an aquatic
type, all the large plate-like appendages of the middle region of
the body (mesosoma), with the exception of the first, being
furnished with branchial lamellae. There are two orders.

Order 1.—Xiphosura (King-crabs).

None of the appendages of the prosoma are paddle-like in
form in the Xiphosura. The segments of the opisthosoma do not
G

82 Guide to Arachnida.

Table-case exceed ten in number. The American King-crab (Xiphosura

No. 18.
Wall-case
No. 7.

polyphemus) differs from the Oriental species in having the
terminal segment of the inner branch of the genital operculum (on
each side) retained as a free movable lobe, whilst in the Oriental
genera (Tachypleus and Carcinoscorpius) it is suppressed. The
three genera which have resulted from the subdivision of the old
genus Limulus are referable to a single family, Xiphosuridae.

The King-crabs are marine, shore-frequenting forms. They live
in water of moderate depth, burrowing in the sand at the bottom,
and their food consists of bivalves, worms, etc. They occur on
the Eastern coast of North and Central America, and in the

Fig. 54.

The American King-crab (Xiphoswra polyphemus),

About 51, the diameter of the animal.

Oriental seas from the Bay of Bengal to the coasts of China and
Japan, Torres Straits, etc. A number of small Palaeozoic
forms (e.g. Belinurus and Hemiaspis, of which figures are shown
in Table-case 18) are known, which seem to be intermediate in
structure between the Xiphosura and the Trilobites. Forms
which resemble the modern type of Xiphosura first appear in the
Triassic rocks. Several specimens of King-crabs from the
Solenhofen stone (Jurassic Period) are shown in the Geological
Department. (Gallery 8, Wall-case 13c.)

A large example of a King-crab (Tachypleus tridentatus) from
British North Borneo is displayed in the upper part of Wall-case 7,
and representatives of the three genera are shown in Table-case 18.

oe)
Oo

Gigantostraca.

Order 2.—Gigantostraca (Eurypterines).

In the Gigantostraca the sixth (or fifth and sixth) pairs of the ieee
appendages of the prosoma are modified to act as paddles. There
are twelve distinct somites in the hinder region of the body

(mesosoma and metasoma).

Athi tes toys)

Restoration of Huwrypterus fischeri (after Holm). A—Appen-
dages of prosoma. B—Sternal plate of prosoma. c—Appendage
believed to distinguish the female sex, perhaps an ovipositor.
p.—Plate-like appendages of mesosoma. The first plate (which
corresponds to two somites of the body) is the genital oper-
culum, E—Sternal plates of metasoma.

Ga,

Table-case
No. 19.

Table-
cases Nos.
19, 20.

Guide to Arachnida.

CO
=

The members of this order became extinct in Palaeozoic times.
They have been found chiefly in the Upper Silurian, but are
known to extend upwards as far as the Carboniferous. They
were free-swimming forms, probably marine.

A model of one of the Gigantostraca (Hurypterus fischerv) is
exhibited between Table-cases 16 and 17, in the Insect gallery.
The fossils from which this model has been reconstructed are
found in limestone of Upper Silurian age on the island of Oesel
in the Baltic, and are remarkable from the fact that the chitinous
substance of the outer coat of the animal has been preserved
unaltered in chemical and physical composition. It has been
possible to dissolve the remains out from the rock and to mount
them as microscopic preparations. As a result, it can now be said
that the structure of this species is better known than that of any
other extinct Arthropod. Specimens and drawings further illus-
trating the group are exhibited in Table-case 19. Reference must
be also made to the large specimens of Pterygotus and to the
model of Stylonurus, which are placed on the wall (between
Cases 12 and 13, and 13 and 14) in the Geological Department.

Division B.—HMBOLOBRANCHIA.

The grade Embolobranchia contains the air-breathing forms of
Arachnida, in which respiration is carried on by internal pulmonary
sacs or tracheal tubes. _There are nine orders.

Order 1.—Scorpiones (Scorpions).

The members of this order are remarkably uniform in structure.
The prosoma (‘‘cephalothorax’’) is covered by an unsegmented
carapace, which bears from two to five lateral eyes, besides the
paired median eyes. The first two pairs of appendages are in the
form of pincers, the first pair or chelicerae being small and three-
jointed, whilst the second, or palps, are very large and have six
joints. All four pairs of legs are of the walking type and are
furnished with paired movable claws. The mesosoma, like
the metasoma, consists of six distinct somites, and the five
posterior of the latter region are narrowed to form the tail,
which also includes the post-anal sting. A pair of curious comb-
like organs, the pectines, tactile in function, are present on the
lower surface of the second mesosomatic somite. The respiratory
organs consist of four pairs of lung-books, the cavities of which

Scorprones. 85

are filled up with lamellae, which are arranged like the leaves of a Table-
book. cases Nos.
: : 19, 20.

A number of species possess sound-making organs, which are
usually situated between the chelicerae or between the palp and
the first leg.

The scorpions are a very ancient group. Fossil species which
closely resemble the living forms have been found in strata of the
Silurian age. They differ from the Carboniferous and _ recent
species chiefly in that the ter-
minal segments of the legs are
thicker, and that the tips of the
legs are bluntly pointed and
without movable claws.

In the Geological Department,
specimens of the Carboniferous
scorpions (Hoscorpius and Cyclo-
phthalmus) are exhibited in
Gallery 8, Table-case 23, and
Wall-case 13c.

At the present time scorpions
are found in all the warmer
regions of the world. Several of
the West African and Indian
species (Pandinus and -Palam-
naeus) are of very large size,
one or two of them reaching a
length of about nine inches.
There are several Huropean
species, the largest of them
belonging to the genus Buthus,
which has two representatives in
Europe. One of these (Buthus
occitanus) is common in the South of Europe and also occurs
in the North of Africa, and the other is found in Greece.
Another member of the Buthidae (Butheolus melanurus), which is
of small size, lives in Sicily. The little black scorpions of the genus
Euscorpius are abundant in the south of Hurope. They live under
stones and in other obscure situations, and sometimes make their
way into houses in the wet weather; there are four Kuropean
species. An allied genus (Belisarius), with a single species,
which has lost all trace of eyes, is restricted in distribution to the
Eastern Pyrenees. One of the Buthidae (Jsometrus maculatis)

Fra. 56.

Buthus occitanus (slightly reduced).

Table-
cases Nos.
19, 20.

86 Guide to Arachnida.

has been introduced into all the warmer regions of the world, and
is found in oceanic islands.

Scorpions are carnivorous, feeding chiefly on insects. As is
well-known, they are poisonous; the poison-glands, which are
paired, are situated in the terminal bulb of the tail. The larger
species mostly construct deep burrows with their pincers, others
live in shallow excavations under stones or under the bark of
fallen trees.

A representation of the burrows of the common Egyptian
scorpion (Buthus quinquestriatus) is placed in Wall-case 7.

The young of scorpions are born fully formed, but in some
species at least they are still enclosed within the egg-shell at birth
and are liberated by their mother or by their own efforts. Until
they are able to shift for themselves they are carried about on the
back of the mother; a female example of a South American
scorpion (Centrurus margaritatus), carrying its family on its back,
is exhibited in Table-case 19.

The classification of the scorpions is still in an unsettled state ;
the recent species are arranged by Mr. Pocock in four families :
1. PanprnIDAE. 2. BOTHRIURIDAE. 3. VEJOVIDAE. 4. BUTHIDAE.

A representative series of scorpions is displayed in Table-
case 20.

Fam. 1.—Pandinidae.

This family, which contains the largest of the existing
scorpions, is found in Africa, South Asia, Australia, and South
America. It is characterised by having the sternum of the
cephalothorax pentagonal in shape, and by the presence of only
a single pedal spur upon the feet. (Genera: Pandinus, Opisthoph-
thalmus, Urodacus, etc.)

Fam. 2.—Bothriwridae.

This family is confined to South America and Australia. It is
characterised by haying the sternum strongly compressed antero-
posteriorly, and reduced to a short but wide transversely-lying
plate. There are two pedal spurs on the feet. (Genera: Bothri-
urus, Cercophonius, etc.).

Fam. 3.—Vejovidae.

The representatives of this family are found in South Europe,
Asia, and North and South America, but are entirely unknown in

Pedipalpr. 87

tropical Africa, Madagascar, and Australia. The sternum is Table-

pentagonal, as in the Pandinidae, but is variable in form, being ses
sometimes much wider than long, sometimes as long as wide. ~~
The presence of two pedal spurs upon the feet furnishes the best
character for distinguishing the Vejovidae from the Pandinidae.

(Genera: Vejovis, Iurus, Huscorpius, Broteas, etc.).

Fam. 4.—Buthidae.

The Buthidae, which are universally distributed to the South
of about the 45th parallel of North latitude, are distinguished from
the Vejovidae by the triangular shape of the sternum and by the
bifurcation of the anterior pedal spur. (Genera: Buthus, Cen-
trurus, Isometrus, etc.)

Order 2.—Pedipalpi (Whip-scorpions and their allies).

The cephalothorax (prosoma) in these Arachnida is covered Table-case
dorsally by a carapace, which is sometimes segmented posteriorly. Bos 20
A deep constriction separates this region of the body from the
abdomen (opisthosoma), which has eleven somites. The palps are
of large size and are chelate or sub-chelate in form. The third
appendage (first leg) is longer and more slender than the remain-
ing legs, and has the terminal segment (or segments) sub-divided ;
it is used as a feeler. There are no poison-glands in these
animals.

These Arachnids are inhabitants of the warmer parts of the
globe. They are found in damp places under stones or fallen
leaves, in the crevices of rocks, and in other similar places.
Several fossil species have been discovered in the Carboniferous
strata. The Pedipalpi are divided into two sub-orders.

SuB-orDER I.—UROPYGI.

In these Pedipalpi the cephalothorax is longer than wide. The
tarsi of the third pair of appendages are divided into eight or nine
segments. There are two tribes.

TrinE— UROTRICHA.

Uropygi in which the carapace is unsegmented and bears well-
developed eyes.
On account of their long and many-jointed tail and of their

88 Guide to Arachnida.

Table-case Superficial resemblance to scorpions, the Urotricha are known as

No. 21.

Whip-scorpions. All the known genera (which number ten) are
referred to the family Thelyphonidae, which is now restricted

ce

Wag

ray

a

\

~
<
Z{

as
ARAB

Ne

‘

ft 4a

\\

fo

Fia. 57.
Whip-scorpion (Thelyphonus caudatus), x 2.

to South-Eastern Asia and Tropical America. Of the genera,
Thelyphonus, which is widely distributed in the Oriental region,
is the richest in species. The largest known species of The-
lyphonid (Mastigoproctus giganteus), a species which is found
in the southern part of North America, sometimes reaches a
length of more than two and a half inches. In the Carboniferous
period the family was represented by the genus Geralinura,
which has been discovered both in Europe and in North
America.

Whip-scorpions live beneath stones or fallen tree-trunks, or in
burrows in the soil. They feed mostly on insects, which they

Pedipalpr. 89

crush with their powerful pincers. When irritated they eject an Table-case
offensive acid secretion, which is the product of two large glands i ae
opening on the end of the last abdominal segment. The female,

after laying her eggs, carries them about attached to the under side

of her body.

TrRine— TARTARIDES.

The carapace of the cephalothorax is segmented posteriorly ;
it sometimes bears a pair of lateral eye-specks, but these are
often obsolete or absent. The tail is short and is unsegmented
in the male sex, whilst in the female it has three or four joints.

The Pedipalpi belonging to this tribe, which contains the
single family Schizomidae, are small in size and show traces of
degeneration.
They live under
stones and vege-
tation in the
tropical parts of
Africa, Asia and
America. Two
genera (Schizo-
mus and Trithy-
reus) are known.

Drawings of a
Tartarid (Schizo-
mus — Crassicau-
dus), to illustrate
the morphology
of the group, are
placed in Table-
case 21.

Sus-orpDeErR II.
AMBLYPYGI.

The cephalo-
thorax of these
Pedipalpi is wider

than long. All Fic. 58.
the segments of Damon johnstoni (one-half natural size).

the legs of the
first pair, with the exception of the basal three, are sub-divided so
as to form a long flagellum.

Table-case
No. 21.

90 Guide to Arachnida.

The Amblypygi were represented in the Carboniferous period
by the genus Graeophonus. At the present time they are confined
to the warmer parts of Africa, Asia and America, the largest
species, which belong to the genera Damon and Heterophrynus,
being met with in the tropical forests of West Africa and Brazil.
By the flatness of the body and by the lateral projection of the legs,
they are admirably fitted for living under stones and the loosened
bark of fallen trees or in the crevices of rocks. The Amblypygi of
the section Charontinae live in caverns. The feeding and breeding
habits of the Pedipalps of this sub-order are similar to those of the
Whip-scorpions.

There is a single family Tarantulidae, with ten genera, none
of which are very numerous in species.

Order 3.—Palpigradi.

A carapace, which is divided into three segments (the large
anterior one of which represents the terga of the first four somites),
covers the cephalothorax (prosoma) in the
Palpigradi. The appendages of the first pair
are large, chelate and three-jointed; those
of the second slender, like the remaining pairs,
and armed with three claws. A narrow waist
separates the cephalothorax and abdomen
(opisthosoma) from one another. There are
ten abdominal somites, which are not divided
into dorsal and ventral plates, and the last
three of them are narrowed to form a flexible
support for the long many-jointed post-anal
flagellum. Respiratory organs are absent.

These interesting Arachnids were first dis-

babe —__—. covered by Professor Grassi, who described
Fie. 59. and figured an Italian species in the year
Koenenia mirabilis 1885. They are minute creatures, usually

(magnified). measuring less than two millimetres, or
barely one-twelfth of an inch in length. All
the known species belong to the genus Moenenia, which has been

discovered in South Europe, Tunis, Siam, Texas, Chile and ~

Paraguay. They are blind, practically colourless animals, living
in damp earth or under moist leaves, under stones, or in caves.

Several drawings of Koenenia mirabilis are on view in Table-
case 21.

Araneae. 9]

Order 4.—Araneae (Spiders).

The carapace of the cephalothorax (prosoma) is unsegmented Table-

in the spiders, and the eyes are situated in the middle of its {
anterior margin; they are usually eight in number, and are
typically arranged in two transverse rows, but there are many
other arrangements in the various families. The first appendages
or chelicerae consist of two segments, the basal one of which
contains the poison-gland, whilst the apical one forms a retroverted
fang. All the remaining appendages are leg-like in form; in the
male a complicated copulatory organ is present on the lower side
of the terminal segment of the second appendage or palp. A narrow
pedicel separates the cephalothorax from the “ abdomen ”’ (opis-
thosoma); with very few exceptions the latter is unsegmented, and
its lower surface is always furnished with a number of spinning
appendages. Two pairs of lung-sacs may be present, but the
posterior pair of these is replaced by tracheal tubes in most spiders,
and in a few species this is also the case with the anterior pair.

Sound-producing organs, which are sometimes very complex in
structure, occur in a large number of Mygalomorph spiders. They
usually consist of arrangements of spines and rods which are
situated on the opposed surfaces of the basal joints of the anterior
limbs (either between the two chelicerae, or between the chelicerae
and the palps, or between the palps and the legs of the first pair).
The presence of a stridulatory organ in these bird-eating spiders
was first made known by Professor Wood-Mason in an Assamese
species (Chilobrachys stridulans). In this spider the inner surface
of the basal segment of the palp is furnished with a row of vibratile
bacilliform bristles and the opposed surface of the chelicera with a
number of strong spines. When irritated the spider assumes
a threatening attitude, raising itself upon its hind legs and
brandishing the front legs in the air, at the same time making an
audible rasping noise by rubbing together the basal segments of
the two anterior appendages.

Another very similar type of stridulatory apparatus is present
in a number of the Arachnomorph spiders of the family Szcaridae
(in the genera Sicarius and Scytodes). The inner surface of the
femur of the palp in these spiders bears a single tubercle (or a
longitudinal row of tubercles), whilst the outer surface of the
chelicera is provided with a series of well-marked transverse ridges.
The noise made by the spiders of this family has been compared to
the buzzing of a bee.

cases Nos.

29, 23.

92? Guide to Arachnida.

Table- Mention must also be made here of the curious sound-producing
OS organs which are found in many of the Theridiidaec. These spiders
’" "have the anterior part of the abdomen especially hollowed out and
hardened, the surface of this concavity being armed with teeth or
ridges which can be moved against the granular or striated surface
of the posterior end of the cephalothorax. In several of the
Agelenidae also an analogous structure occurs, but the structures
on the abdomen are rubbed against an enlarged tooth-like projec-
tion, which is present on the pedicel separating the cephalothorax

from the abdomen.

Spiders are oviparous. They construct a ‘ cocoon” (or several
cocoons) for the protection of the eggs, and this usually consists of
several layers of silk, the outermost coat in many cases being of
especial strength or thickness. Many species seem to give but little
or no attention to their cocoon when once it has been completed.
Very often, however, the mother watches over it with extreme
solicitude until the young spiders emerge, and displays great
courage in its defence in times of danger. Special tents or cells
of silk for the reception of the cocoon are constructed by many of
the spiders which lead a wandering life, and by the tube-spinning
spiders (see Wall-case 7). In these cases the mother shuts herself
up with the cocoon, remaining within on guard until the eggs
hatch. A large number of spiders which lead a predatory life
(Lycosidae, ete.) carry the cocoon about with them, either in their
chelicerae or attached to their spinnerets.

The dispersal of the young of Araneids, which usually takes place
during the early part of the summer or in the autumn in this
country, is greatly helped by their aeronautic habits. The young
spider climbs to the top of a shrub or other point of vantage and
turns its face in the direction from which the wind is blowing.
It then proceeds to straighten its legs, standing on the tips of them
and elevating its abdomen in the air. One or more threads of silk
now make their appearance, issuing from the spinnerets, and are
drawn out by the wind into long floating lines. At length the
spider lets go and is wafted away through the air, supported by its
air-ship of threads. In his “ Naturalist’s Voyage ’ Darwin makes
the following interesting observation on the ballooning habit of
spiders : ‘“‘ On several occasions, when the Beagle has been within
the mouth of the Plata, the rigging has been coated with the web
of the Gossamer Spider. One day (November 1st, 1832) I paid
particular attention to this subject. The weather had been fine
and clear, and in the morning the air was full of patches of

Araneae. 93

flocculent web, as on an autumnal day in England. The ship was Table-
sixty miles distant from the land, in the direction of a steady nae
though light breeze. Vast numbers of a small spider, about one- ~~
tenth of an inch in length, and of a dusky red colour, were attached

to the webs. There must have been, I should suppose, some
thousands on the ship. The little spider, when first coming in

contact with the rigging, was always seated on a single thread,

and not on the flocculent mass. This latter seems merely to be
produced by the entanglement of the single threads. is

Spiders are divided into two sub-orders: 1. MrsorHELAr.
2. OPISTHOTHELAE.

Susp-OrpER I.—MESOTHELAE.

In the Mesothelae the spinning appendages consist of two Table-case
pairs of biramous limbs, which are situated far in advance of the No. 22.
anus, immediately behind
the pulmonary sacs. The
abdomen is distinctly seg-
mented, the upper surface
being furnished with a
series of eleven tergal plates,
and its ventral surface with
two large plates overlying
the pulmonary sacs, and a
number of small plates
behind the spinnerets.

In the segmentation of
the body and in the position
of their spinnerets, the
Mesothelae differ from all
other living spiders, and
resemble certain extinct

(Carboniferous) types (Pro- Fic. 60.
tolycosa, etc.). There is but Liphistius desultor.

a single family with two

genera (Liphistius and Anadiastothele), which occur in Burma,
Malacea, and Sumatra. Specimens have been captured in the
depths of limestone caverns in Malacca, and it is possible that
the apparent rarity of these spiders is due to their restriction to
a cave habitat. A specimen of Liphistius desultor is exhibited in
Table-case 22.

Table-case
No. 22.

Q4 Guide to Arachnida.

Sus-orpER II.—OPISTHOTHELAE.

The spinning appendages in the members of this sub-order are
situated at the posterior end of the abdomen, just in front of the
anus. All trace of the tergal plates of the abdomen has been lost,
and remnants only of the ventral plates are to be found protecting
the pulmonary sacs.

To the Opisthothelae belong all existing spiders (with the
exception of Liphistius and Anadiastothele), and the majority of
those found fossilised in the gypsum or amber-beds and lacustrine
deposits of the Miocene and Oligocene periods in Europe and
North America.

TRIBE I.—MyYGALOMORPHAE.

In the spiders belonging to this group the posterior pair of
biramous spinning appendages are usually alone retained. The
basal segment of the first appendage projects forwards, the fang
closing backwards upon it. Two pairs of pulmonary sacs are
present.

This group contains the bird-eating spiders ( Mygale”’) and
trap-door spiders and their allies, which are nearly all confined to
the tropical or warmer temperate regions. There are a number
of families, the more interesting of which are briefly described

below.

Fam.—A vicularudae.

The spiders of this family have the tips of the legs and the
under surface of the terminal joint (or joints) of the legs furnished
with a dense pad of iridescent hairs. Digging spines are not
present on the chelicerae.

The large, hairy spiders, which are commonly known as
“ Mygale,” or bird-eating spiders, belong to this family. A West
Indian species (Psalmopoeus cambridg?) is sometimes found con-
cealed in the bunches of bananas which are imported into this
country. Some of the South American species (Theraphosa,
Xenesthis) reach a very large size, and are the largest known spiders.
They are nearly all tropical forms. So far as is known, none of them
spin regular snares; many of them, however, construct a silken
funnel at the entrance to their nests. In an allied family, the
Dipluridae, the entrance is surrounded by a large flat web, which

Araneae. 95

is very similar in appearance to that of an Agelenid spider. The Table-case
Aviculariidae live in hollow trees, under stones, or in burrows or No.
natural hollows in the ground. The species which excavate a

burrow rarely close the entrance with a trap-door.

The burrows of a South American species (Hphebopus murinus), Wall-case
together with examples of the spider itself, are shown in Wall- N° 7:
case 7. Nests of the common bird-eating spider (Avicularia
avicularia) of the north of South America, constructed in the
hollow trunk of a palm tree, and in the rolled-up leaf of a banana,
are also shown in this Wall-case, and specimens of the spider, and
also of other species of bird-eating spiders, are placed in Table-
case 22.

Fam.—Ctenizidae.

In the Ctenizidae the feet are not furnished with apical tufts
or pads of hair. The chelicerae are furnished with digging
spines.

On account of their neatness and of the ingenuity displayed
in their construction, the trap-door nests of these spiders have
long attracted attention. The nest takes the form of a long
tunnel in the ground, the interior of which is lined with
smooth silk, the entrance being often closed by a_ neatly
fashioned trap-door, the outer surface of which exactly matches
its surroundings, so that it is practically invisible when closed.
The spider often constructs one or more side chambers to
the burrow, and sometimes shuts them off from the main
part of the tunnel by additional trap-doors, thus ensuring a
place of refuge in case the outer door is forced by an enemy.
Some of the species, which do not close the entrance to the nest
by a trap-door, erect a turret of grass or small twigs, bound
together by web, around it. In some instances (Psewdidiops, ete.)
the trap-door spider constructs its nest on the trunk of a tree,
spinning a silken tube in the crevices of the bark, and overlaying
it with chips of bark and lichen, so as to strengthen its walls and
to conceal it from view (Table-case 22). Most of the spiders of
this family have the carapace and limbs smooth and polished, and
the abdomen clothed with short dense hair, so that no impediment
is offered to rapid movement in the silk-lined burrow.

Two burrows of a trap-door spider (Actinopus wallacet), from Wall-case
Brazil, are exhibited in Wall-case 7. In one of them the spider No. 7.
is cautiously raising the lid, on the watch for approaching prey.

Table-case

No. 22.

Wall-case
No. 7.

Table-case
INOS 23!

96 Guide to Arachnida.

Fam.—Atypidae.

The two genera (Atypus and Calommata) which compose this
family differ from the Aviculariidae and Ctenizidae in possessing
a large maxillary process upon the base of the palp. The chelicerae
are not usually furnished with digging spines.

The genus Atypus has a wide distribution, occurring in
Europe, North Africa, Japan, Burma, and Java; whilst Calommata
is found in Japan, Burma, the Sunda Islands, and West Africa.

The only Mygalomorph _ spider
which occurs in this country (Atypus
affinis) belongs to this family. It is
found in the South of England, the
Channel Islands, and also in Ireland,
and many places on the Continent.
The nest of this spider consists of a
long burrow, excavated in the ground,
and lined throughout with web. This
lining is continued beyond the surface
as a long closed tube, which is either
attached to some object near at hand

Fig. 61. or lies loosely on the surface of the
Atypus affivis. x 2. eround; when flies or other insects

alight on it they are seized from within
by the spider, and pulled through the silk, the rent thus made
being repaired afterwards. Similarly, the male enters the burrow
by biting a hole in the wall of the tube.
A number of the external tubes of the North American purse-
web spider (Atypus abbot), which are spun against the trunk of a
tree, are exhibited in Wall-case 7.

TRIBE 11.—ARACHNOMORPHAE.

In these spiders the outer branches of the anterior pair of
spinning appendages and both the outer and inner branches of
the posterior pair are present, the inner branches of the anterior
pair being often represented by a perforated spinning-plate (the
“ cribellum’”’) or by a membranous lobe (the ‘“colulus’’). In the
spiders in which the ‘“cribellum”’ is present, the penultimate joint of
the fourth leg is always furnished with a series of curved hairs. The
chelicerae project downwards. The posterior pair of pulmonary’
sacs is replaced (except in the genus Hypochilus) by tracheal tubes,
the stigmata of which may be situated immediately behind those of

Araneae. 97

the anterior pulmonary sacs, but more usually unite to form a Table-case

common aperture in front of the spinning appendages. No. 23.
The great majority of spiders belong to this group, and the

habits are very varied in the different families. Many of the

species obtain their prey by means of webs, others by stealth or

by running it down. <A number of species lead an aquatic or

semi-aquatic life. In most of the Mygalomorph spiders, and those

of the Arachnomorph spiders which live a free, wandering life,

the silk is only used for the fabrication of the cocoon or for lining

the nest. The snares of the sedentary or web-spinning spiders

vary much in structure in the different groups; sometimes they

consist of a few crossing lines only, whilst in other cases, as in

the orb-spinners (Argiopidae), they are of marvellous symmetry

and beauty. There are numerous families; some of the more

important of these are commented upon below.

Fam.— Argiopidae (Epeiridae).
The spiders of this family are sedentary in habit, catching their
prey by means of webs. Some of them spin orb-webs, others

Fia. 62.

Gasteracantha formosa (slightly enlarged). (After Vinson.)

construct horizontal sheets of web or irregular networks. The
Species are very numerous, and present much diversity of form
and colouring, many of them being of exceeding beauty. Of the
species occurring in this country, the large garden spider (Aranea
(Hpeira) diademata) is familiar to everyone, and a number of
smaller forms are also abundant. The species of Nephila are the
largest Argiopid spiders. They are confined to the warmer parts
of the world. Their immense orbicular webs, covering several feet
in area, are composed of silk strong enough to arrest the flight of
small birds, which, becoming entangled, are killed and eaten by
the spider. Their food consists for the most part, however, of
grasshoppers and other insects. The male is ridiculously small as
compared with the female. On account of his small size and
great activity he is able to make his escape from her if she
H

Table-cage
No. 238.

98 Guide to Arachnida.

turns upon him with murderous intent during
courtship, as female spiders commonly do.

Some of the tropical Argiopidae (Gasteracantha,
ete.) ave the abdomen hardened and armed with
long spines. It is believed that these are of ad-
vantage to the spider by rendering it unpalatable
to birds. The male of Gasteracantha, which is
much more retiring in its habits than the female,
is not furnished with spines. Remarkable illustra-
tions of protective resemblance are afforded by
some of the species belonging to this family,
as, for instance, the Rhodesian species known
as Caerostris corticosa. In colour and general
appearance this spider harmonizes with the bark
of the common Rhodesian thorn-tree, on which it
is commonly found, and its abdomen is furnished

Tarsal-comb of
the fourth leg of
Theridion tepida-
riorum.

Magnified.
(After F. O. Pick-
ard-Cambridge.)

with processes resembling the thorns with which the tree is beset.
The Argiopidae are cosmopolitan in distribution.

Fic. 64,

A Theridiid Spider
(Lathrodectus tredecim - gutta-
tus), Xx 2.

Fam.— Theridiidae.

These spiders differ but little in
structure from the Argiopidae, but
may be readily distinguished from
them by the structure of the fourth
leg, the terminal segment of which
bears a comb of setae (fig. 63).
A few of the species are remarkable
in that they construct no web. The
family is very numerous in species,
and has a wide distribution.

The genus Lathrodectus is, per-
haps, the most noteworthy. of the
Theridiidae. Several of the species
have the reputation of being ex-
tremely poisonous, and numerous
accounts of the effects of their
bite have been published. The
abdomen in the poisonous species

is marked with conspicuous red stripes or spots. A coloured draw-
ing of the well-known European species (Lathrodectus tredecim-
guttatus) is exhibited in Table-case 23.

Araneae. 99

Fam.—Thomisidae.

The Thomisidae, or Crab-spiders, as they are often called on Table-case
account of their sidelong method of walking, are usually small, No. 23.
squat-looking spiders. They lead a wandering life, and do not
construct regular snares. Many of them are sluggish in habit,
and are noticeable for their protective coloration, which renders
them inconspicuous to their enemies, and at the same time enables
them to hie in wait for and
surprise their prey. The
species which live in
flowers are said to be able
to change their tints to
suit the blossom on which
they are resting; other
Thomisids show close re-
semblance to various sub-
stances such as_ bark,
blades of grass, the ex-
crement of birds, ete. The
Crab-spiders belonging to
the sub-family Philodro-
minae are more active in
habit, and trust to their
speed for the capture of

\
\
\

haa are Fig. 65.
eee : Flower-spider, Miswmena vatia, x 2.
A sketch in colour of (After Blackwall.)

a common British flower-
spider (Miswmena vatia) is exhibited in the Table-case containing
the specimens of Arachnomorph spiders.

Fam.—Clubionidae.

The spiders of this family are often of large size, but there are
a great number of small or medium-sized species. ‘They are pre-
datory forms, and are provided with large and powerful chelicerae.
Many of them are laterigrade, and can walk either backwards or
sideways at will. In the tropical regions of the world a number
of large species are met with in houses, and several of them have
a wide distribution. One of these house-spiders (Heteropoda regia)
has been imported by shipping from the East Indies practically all
over the world, and, like the common rat and cockroach, main-
tains itself wherever the conditions are favourable to its survival.

H 2

100 Guide to Arachnida.

Table-case Specimens of this spider have been found at University College,

No. 23.

London, and also at Bristol, but since tropical conditions appear
to be essential to its existence, there is little likelihood of its
becoming an established species in this country. Some of the
smaller forms are remarkable for the closeness with which they
mimic ants. The Clubionidae are cosmopolitan in distribution.

Fam.—Lycosidae.

On account of their predatory habits these spiders are commonly
known as wolf-spiders. With the exception of the species belonging
to the group Hippaseax, which spin large webs, accompanied by
tubular retreats, similar to those of Agelena and its allies, they do
not construct snares. The majority of the Lycosidae do not
make a regular nest; a number of species, however, construct
burrows in the ground similar to those of the trap-door spiders,
and some of them surround the aperture with a tower of twigs
(e.g. Lycosa arenicola, » species which occurs in the United
States, exhibited in Wall-case 7) or grass, or even close it with
a neat trap-door. The female spider carries the cocoon about
with her, attached to the spinning mammillae. On leaving the
cocoon the young spiders climb on to the back of the mother,
attaching themselves by threads, and are carried about by her in
this fashion for several days. The spider encumbered thus by her
living burden presents an interesting and curious spectacle.

The name “ Tarantula” is loosely applied to many large spiders
of various kinds. It should really be restricted to the Italian
species Lycosa tarentula (and its allies), which first received the
name from its abundance near the town of Taranto or Tarentum.
Amongst the Italian peasantry there still prevails an ancient
superstition that the poisonous bite of this spider gives rise to a
sickness called Tarentism. The chief specific for the malady is
music, which incites the victim to dance in a frenzied and violent
manner, and to continue the exercise until the outbreak of a pro-
fuse perspiration effects the cure by getting rid of the poison.

Fam.—Agelenidae.

These spiders are sedentary web-spinning forms. Their snare
usually consists of a large horizontal sheet of web, with one or
two tubular retreats leading from it. Perhaps the most familiar
of them are the house-spiders (Tegenaria), which construct untidy

Araneae. LO1

webs in the corners of cellars and out-houses. The spiders of the Table-case
genus Desis, which occur on the coasts of South Africa, Malay N° 2°-
Peninsula, Burma, and Australasia, are marine in habit. They

live in holes and crannies in rocks or coral reefs, or under stones

between tide-marks. During high tide they remain shut up in their
waterproof cells of silk, leaving them at low water in search of

prey. Argyroneta aquatica, the Kuropean water-spider, is also a

member of this family. It is found in pools and ditches of fresh

water, and is widely distributed in this country. On account of its
interesting habits it is often kept in aquaria.

Fam.—Hresidae.

With the exception of the species belonging to the genus
Stegodyphus, these spiders are all burrowing forms. In the South
African genus Seothyra the aperture of the burrow is concealed by
a curious four-lobed, flexible flap or mat. The species of Stego-
dyphus live on bushes; some of them are solitary and construct a
sheet-like web accompanied by a tubular retreat; other species
make a large saccular nest of leaves and web, in which hundreds
of individuals live together (the nest of a species from Calcutta is
shown in Wall-case 7). The spiders of this family are confined
to the old world. <A single species (Hresus cinnaberinus) has
been found on two or three occasions in the South of England.

Fam.—Dysderidae.

The members of this family live under stones, the bark of
trees, and other retired places. They do not spin a regular web,
but construct a tubular retreat or cell of silk. Nearly all of them
are inhabitants of temperate or warmer temperate countries.

A coloured drawing of a common British species (Segestria
senoculata) is on exhibition in Table-case 23.

Fam.—Salticidae.

The Salticidae are exceedingly numerous and are nearly always
of small size. They are wandering forms and do not spin webs,
but lie in wait for their prey or stalk it, and then seize it with a
sudden jump. Many of the tropical forms are beautifully coloured ;
the males are often more vividly coloured than the females, and
their antics when courting are often of a very curious nature. They
execute intricate movements and dances before the females, moving
so as to display to advantage their beauty of form and colouring.

102 Guide to Arachnida.

Table-case Of the British jumping spiders, Hpiblemwm scenicum, a species

No. 23. which lives in the crevices of walls, is the most frequently met
with. It is often to be seen wandering about in the sunshine in
search of prey.

It is to this family that the majority of the ant-like spiders
belong. In the principal genus Myrmarachne there are more than
eighty species, which are distributed over the temperate and
warmer regions of the world. They often mimic particular

species of ants,
resembling them
closely in form and
colour; their gait
also is very ant-like,
and they habitually
run in the zigzag
fashion of an ant
pursuing its prey. To
complete the decep-
tion, the legs of the
first or second pairs
in some species are
held up in the air
so as to simulate
the antennae of the
insect. The family
is cosmopolitan in

distribution.
Order 5.
Solifugae (False
Spiders).
' : 2 oe E The Solifugae have
Jumping Spider, Hpiblemum scenicum, x 8. lo
(After Blackwall.) some superficial re-

semblance to the

Table-case spiders, but may be easily distinguished from them by their having
No. 24. both the cephalothorax and the abdomen distinctly segmented and
by the absence of spinning mammillae. The “ cephalothorax”
(prosoma) is covered by three plates. The front one of these,

which represents the terga of the first four somites, is of large

size and bears a pair of median eyes and obsolete lateral eyes.

The ventral surface of the fourth cephalothoracic somite bears a

Solifugae. os)

large pair of stigmata. In nearly all Solifugae the first appen- Table-case
dage is furnished with stridulatory ridges on its inner surface, No. 24.
and in the adult male its dorsal surface is almost always
provided with a curious chitinous structure, the “flagellum,”
which differs much in shape in the various genera. The palp,
which is of large
size, has a suctorial
organ on its terminal
segment. A number
of peculiar chitinous
racket-shaped struc-
tures, the “ malleoli,”
are present on the
lower surface of the
basal segments of the
fourth leg. The
‘“‘abdomen’”’ (opistho-
soma) 1S composed
of ten distinct somites
and the ventral sur-
face of the second
_and third of these is
furnished with paired
tracheal stigmata,
while an additional
unpaired stigma is
often present on the
fourth.

The Solifugae are
typically desert
forms, but a few

species are believed

Inatel, (O7(-

to occur in forests.
After nightfall in the Galeodes arabs (three-fourths natural size).
tropics the nocturnal
species are often found in houses or tents to which they
have been attracted by the artificial light. Many species are
diurnal, and may be seen darting about with amazing speed in
search of prey during the hottest part of the day. They re not
venomous, the mandibles being devoid of poison glands. ‘They
are oviparous.

Solifugae occur in most of the tropical and warmer regions of

104 Guide to Arachnida.

Table-case the world. In Europe they are found in Spain, Greece and

No. 24.

Southern Russia, whilst in America, they are distributed from the
Southern States of the Union to the Andean Chain in Chile and
the Argentine Republic. They are entirely absent from Austra-
lasia, China and Japan.
There are three families:—1. Galeodidae; 2. Solpugidae ;
3. Hexisopodidae.
Fam.—Galeodidae.

In the Galeodidae, the flagellum of the first appendage is
always lancet-shaped. Large hairy claws are present on the legs
of the three posterior pairs. A narrow toothed plate protects the
stigmata of the second and third abdominal somites.

There is but a single genus (Galeodes) in this family. The
species are very numerous and are confined in distribution to the
Old World. They are all quick-running forms.

Examples of Galeodes arabs (Fig. 67), a North African species,
with a wide distribution, are placed in Table-case 24.

Fam.—Solpugidae.

In this family the flagellum presents much diversity of form.
The claws of the three posterior legs are smooth. There is no
toothed plate above the stigmata of the second and third abdo-
minal somites.

There are numerous genera and species of Solpugidae and they
have a wide distribution. The genus Solpuga, which is confined
to Africa, is the richest in species. The majority of the members
of the family are very active in habit, but a number of species
(Rhagodes, etc.) are slow and clumsy in movement.

Fam.—Heaxisopodidae.

These Solifugae have the legs of the fourth pair without claws.
The abdominal stigmata have no plates above them.

The two genera (Hexisopus and Chelypus) which compose this
family are confined to the dry regions of South Africa, and four
or five species only are known. Unlike the great majority of
Solifugae, they are slow-moving forms.

Order 6.—Pseudoscorpiones (False Scorpions).

These Arachnida are very like little tailless scorpions in general
appearance, but in reality they differ from the scorpions in many
important characters. The “ cephalothorax ” (prosoma) is covered

Pseudoscorpiones. 105

by a single plate, which, however, sometimes shows traces of Table-case
segmentation. There are no median eyes, but one or more lateral N° 7+:
ocelli may be present. The fingers of the chelicerae are furnished

with delicate membranous structures called the “ serrula’’ and
“lamina” respectively. The movable finger of the mandible is
furnished with a branched or styliform structure called the “ galea,”

or with a little terminal tubercle; and it is on this structure that

the orifices of the silk-glands debouch. The palps are large and

chelate, as in the scorpions. There is no constriction between the
cepnalothorax and the abdomen (opisthosoma), but the large dorsal

plate of the praegenital segment (which is generally suppressed

in the EKuarachnida) lies between these
two regions. Eleven abdominal somites
can often be distinguished, and noue of
them are narrowed to form a tail, but
the last of them is very small and is
often hidden within the segment which
precedes it.

The Pseudoscorpions are small
Arachnids, which live under stones or
the bark of trees or in moss. They
are occasionally found in houses,
amongst books, ete., and several species
have been found on merchant-ships ;

not uncommonly specimens may be Fic. 68.
met with clinging to the legs of flies or uf
Sms 2 Chelifer cancroides, x 5.

beneath the wing-cases of beetles. One (After Berlese.)

of the British species (Obistwm mari-

dimunv) is found under stones or beneath seaweed below high-water
mark. Their food consists of mites or small insects. At the
breeding season the female envelops herself and her eggs, which
she attaches to the under side of her body, in a spacious silken
cell.

A similar cell is spun as a protection whilst the animal is
moulting and during hibernation.

The earliest-known fossil forms of Pseudoscorpions are from
amber deposits of Oligocene age. At the present day the group
is distributed all over the temperate and tropical countries of the
world.

It is divisible into two sub-orders: (1) Panctenodactyii,
(2) Hemictenodactyli. Drawings illustrating the main points of
difference between these sub-orders are placed in Table-case 24,

106 Cie Ge Ie.

SuB-oRDER I.—PANCTENODACTYLI.

Table-case | The members of this sub-order have the first appendage of
No. 24. small size, and the serrula of the movable finger is fused through-
out its length to the finger.
There are three families: (1) Garypidae, (2) Feaellidae, (3)
Cheliferidae. Specimens of a large species of Chelifer from Sierra
Leone are exhibited in Case 24.

Sus-orpER I]—HEMICTENODACTYLL

‘The first pair of appendages of the Hemictenodactyli is of large
size, and at least the distal end of the serrula of the movable
finger is free.

There are two families: (1) Chthoniidae, (2) Obisidae.

Order 7.—Podogona.

Owing to a close, but superficial resemblance to certain species
of Opiliones the Podogona were regarded, until quite recently, as
forming part of that order. The
anterior of the two plates, which
form the carapace of the cepha-
lothorax (prosoma), is of small
size and forms a movable hood,
which covers the mouth and
first pair of appendages. The
palps are weakly chelate. A
movable membranous — joint
unites the cephalothorax and
the abdomen, the genital aper-
ture opening upon the ventral

Fic. 69. surface of this membrane. The

; abdomen (opisthosoma) consists
Diagram ofa species of Cramtosenna, Gf only four visible: segments,
Podogona. (x 4.) in addition to a tubular ring
encircling the anus. A striking

peculiarity of these animals is the position of the copulatory
organs, one of which is placed at the end of each walking-leg
of the third pair. A single pair of respiratory spiracles, which is
situated towards the posterior end of the cephalothorax, is present.

A specimen of a West African species (Cryptostemma karscht)
(and also enlarged drawings of the species) are also exhibited in
Table-case 24.

Podogona, Opitiones. 107

The existing species of Podogona are referable to the family Table-case
Cryptostemmatidae. They are small Arachnids, barely reaching N° 2+:
half an inch in length, and are confined to the forest-clad tracts of
tropical West Africa and Brazil.

The group was represented in the Carboniferous period by the
genus Poliochera.

Order 8.—Opiliones (Harvest-men).

>

In the Opiliones the ‘“ cephalothorax”’ is confluent with the Table-case
abdomen throughout its width, and its carapace is either unseg- Slee
mented or divided into two segments. Paired stink-glands open
on its dorsal surface near the
lateral margins. The palp is
not chelate. The abdomen is
clearly segmented, the somites
sometimes numbering as many
as ten. Respiration is carried
on, as in the Pseudoscorpions,
by means of tracheal tubes
which open by a_ pair of
stigmata on the sternal plate
of the abdomen.

Most of the Opiliones are
of rather small size, but some
of the South American species
reach considerable dimensions.
They are exclusively carni-
vorous, feeding upon insects,
worms, and the like. ‘The
female lays her eggs in crevices
of the soil, or any damp place, Gonyleptes chilensis.
and leaves them to their fate.

The extinct Arachnida known as the Anthracomarti, which
occur in the Carboniferous strata, are perhaps allied to the Opiliones.
A cast and drawings of one of these fossil forms are exhibited in the
Table-case (No. 25) with the Opiliones, and several casts and
specimens are shown in the Geological Department (Gallery 8,
Table-case 23).

Fia. 70.

Sus-orDER I.—LANIATORES.

In these Opiliones the palp is often stout and furnished with a
strong prehensile claw. There is a single claw on each of the

108 Guide to Arachnida.

Table-case legs of the first pairs, but the legs of the posterior pairs have

No. 25.

two claws (except in the family Triaenonychidae, in which all
the legs are furnished with a single claw, which differs, however,
from that of the Palpatores in being armed with lateral processes).

The Laniatores (see Fig. 70) are divided into a number of
families and have a wide distribution ; they are mostly tropical
forms and are especially numerous in South America. A few
small species occur in Europe and North America.

Sus-orpER IJ.—PALPATORES.

In the Palpatores the palp is slender and the claw is small and
weak ; it is used as a tactile organ. A single claw is present on
the legs of all four pairs.

The sub-order Palpatores, which is cosmopolitan in distribution,
and comprises almost all the European species, is the only one
which has representatives in Great Britain. There are twenty-
three or twenty-four British Opiliones, and nearly all of them
belong to the family Phalangiidae. One of them (Phalangium
opilio) is common on walls, and other species are abundant under
stones, amongst herbage, grass, ete.

Perhaps the most remarkable of the
members of this sub-order are those be-
longing to the family Trogulidae. They
are hard-skinned forms and have the
front part of the cephalothorax produced
forwards to form a hood, which conceals
the mouth and chelicerae. Two genera
(Anelasmocephalus and Trogulus) belong-
ing to this family have been found in this

country.
Fig. 71. Sus-orDER IIJ.—ANEPIGNATHI.
stylocellus s tranus. : ae
see one Sieg One of the most important distin-

cuishing characters in these Opiliones is
the position of the orifices of the stink-glands, which are placed
on the summit of prominent cones or tubercles. By the earlier
students of the group these cones were mistaken for stalked eyes.
The palp is slender and its claw minute.
There is a single family, the Szronidae, the members of which
chiefly occur in the Hast Indies and Ceylon. <A species has also
been found in South Africa, and another on the West Coast of

Acari. 109

Africa. In Europe they are known from Austria, France and Table-case

Corsica. Nae
Drawings of Stylocellus suwmatranus, to illustrate the structure

of the Anepignathi, are exhibited in Table-case 25.

Order 9.—Acari (Mites and Ticks).

These Arachnida, which show many traces of degeneration, Table-
are most closely allied to the Opiliones. The cephalothorax and Sac ontoe
abdomen are completely fused with one another, and the latter ~ ,
region is usually without any trace of segmentation. The appen-
dages of the first pair vary in structure, being sometimes chelate,
sometimes styliform, and often retractile beneath the fore border
of the cephalothorax; the basal segments of the appendages of
the second pair are fused beneath the mouth and project forwards
below, uniting laterally with the “ camarostome,” or “ rostrum,” to
form a suctorial proboscis.

The Acari are mostly of small, or even microscopic size. Some
live a free and predatory life ; others are parasitic for the whole or
part of their lives upon plants or animals.

From an economic standpoint many of the Acari are of con-
siderable importance on account of the injury they inflict upon
plants; and the Ticks are now known to be of great importance
in the transmission of certain diseases of man and domesticated
animals, more especially in tropical countries.

They are divisible into the following sub-orders :—

1. Notostigmata. ). Astigmata.

2. Cryptostigmata. 6. Vermifornua.
3. Metastigmata. 7. Tetrapoda.
4. Prostigmata.

Sus-orpER I.—NOTOSTIGMATA.

In the Notostigmata the abdomen consists of ten segments,
which are defined by grooves in the integument, the four anterior
of them being furnished dorsally with paired tracheal stigmata.
To this sub-order belongs the single family Opilioacaridae.

These mites have been found under stones in Algeria, Italy,
Arabia and South America. They are not parasitic.

A drawing of Opilioacarus seqmentatus is exhibited in Table-
case 25.

Table-case
No. 25.

Table-case
No. 26.

10 Guide to Arachnida.

Sus-orDER II].—CRYPTOSTIGMATA.

Acari with the tracheal spiracles situated in the articular
sockets of the four pairs of locomotory appendages. The integu-
ment is thickly and continuously chitinized, and shows no sign of
segmentation.

This sub-order contains the single family Oribatidae, sometimes
known as beetle-mites, on account of their hard, black, shiny
integument. They are not parasitic, but live in moss, under stones,
etc., in damp places.

An enlarged drawing of an Oribatid mite (Notaspis bicolor) is
on view in Table-case 25.

Susp-orpDER IJI.—METASTIGMATA.

Acari with the tracheae opening by a pair of stigmata, situated
above and behind the base of the fourth or fifth or sixth pair of
appendages. This sub-order contains two families: Gamasidae,

Ixodidae.

Fam.—Gamasidae.

There is no serrated beak in
these mites.

They live for the most part a
non-parasitic life in damp or moist
localities, and prey upon organisms
smaller than themselves. Many
of them are found habitually upon
large insects, lke beetles, but
apparently for the purpose of loco- _
motion, not of parasitism. Some
members, however, are parasitic
upon mammals and birds.

Bie., 72.

Fam.—Ixodidae.
Gamasus coleoptratorum (mag-
nified). (After Berlese.) The coalesced basal segments of

the appendages of the second pair

are produced in front into a cylindrical piercing process, or beak,

furnished with recurved teeth. The appendages of the first pair
are still pincer-like, but are much modified.

The Ixodidae, or Ticks, live as temporary parasites upon

mammalia, birds and reptiles, whose blood they suck by burying

their mandibles and beak in the skin. The females quit their host

Acari. all

to lay their eggs upon the ground, under stones, in grass, the crevices Table-case
of walls, ete. The Ixodidae are divided into two sub-families. No. 26.

Besides the specimens of Ixodidae exhibited in Case 26, a few
specimens are on view in the North Hall.

SuB-FAM.—Argasinae.

In the Argasinae the jaws are overlapped by a forward expan-
sion of the body, and the skin is leathery and coriaceous ; the male
and female are very similar in appearance (Genera: Argas and
Ornithodoros).

The Argasinae are chiefly parasitic on human beings, birds,
and bats. The human tick-fever of
tropical Africa (Spirillosis) is conveyed
by the species known as Ornithodoros
moubata; the fowl-tick (Argas per-
sicus) is also known to transmit
spirillosis amongst its hosts.

Sus-FAM.—Ixodinae.

The mouth-parts of the Ixodinae
are terminal. The skin is smooth;
a firm chitinous shield covers the
whole of the back of the male, but
leaves a considerable portion of that
of the female uncovered.

Several of the members of this Pia. 73.
family are known to convey infectious mea Sa ee eae
diseases ; perhaps the most important (After Salmon and Stiles.)
of these is the cattle-tick (Margaropus
annulatus), a widely distributed form, which is the carrier of
Texas-fever (Piroplasmosis).

Sus-orpER IV.—PROSTIGMATA.

Acari with a single pair of tracheal stigmata, which are situated
on the anterior part of the body (except in the Halacaridae, in
which the tracheae are absent).

The Acari of this group differ greatly in their habits; most of
them are free-living and are found in moss, under stones, on
plants, etc. They chiefly feed upon vegetable substances, but
many of them prey on minute animals. There are four families:
Trombidiudae, Hydrachnidae, Halacaridae, and Bdellidae.

Table-case
No. 26.

TAZ Guide to Arachnida.

Fam.—Trombidiidac.

The Trombidiidae are soft-skinned mites, the palpi are free,
the penultimate (or, more rarely, the last) segment being armed
with a claw.

Most of the mites of this family are free-living forms, which
are either predatory or herbivorous. A few species are parasitic
upon vertebrates and insects. The species of Trombidium are
clothed with long, red, velvety hair, and present a striking appear-
ance. The European representatives of the genus are of small
size ; in the tropics, however, large species, measuring about half
an inch in length, occur. The harvest-bugs, which cause irritation
in autumn by burrowing under the skin, are six-legged larvae
belonging to various species of Trombidiidae. The spinning-mites
(Tetranychinae), which occur in immense numbers on yarious
kinds of plants, cause much damage to vegetation. They spin a
fine web, which is usually found coating the lower side of leaves.
The bright glaze, which may sometimes be seen on the trunk
and branches of the lime tree, is produced by one of these mites
(Tetranychus telarius).

Fam.—Hydrachnidae.

The Hydrachnidae, or water-mites, resemble the Trombidiidae
closely in structure. The legs are furnished with swimming-
hairs.

Most of the Hydrachnidae live in fresh water, but there are a
few marine species. Their food consists of small crustacea, insect
larvae, infusoria, ete. They are widely distributed and there are
numerous British species.

Fam.—Halacaridae.

In the Halacaridae the buccal organs are carried on a distinct
rostrum; the appendages of the first pair are either stylitorm or
chelate, and the terminal segment of the palp is conical or styli-
form. The skin is strengthened by a number of dorsal and ventral
plates.

These mites are chiefly marine in habit, but a few species occur
in fresh water. They do not swim, but crawl on algae and marine
animals. They were first made known by Mr. Gosse, who
described several British species in the year 1855.

Fam.—Bdellidace.

The members of this
family are soft-skinned
mites, with a distinct
rostrum. The first pair of
appendages are in the form
of pincers and the palps
are slender and unarmed.

These mites are free-
living terrestrial forms,
which lead a_ predatory
life. There are a number
of British species. <A
little red species (Bdella
littoralis) 1s common on
our sea-coasts.

SUB-ORDER V.
ASTIGMATA.

In these Acari, which

Acart. tL3

BiG. 14.

Sarcoptes scabiei, the itch mite, x 100
(after Canestrini).

are closely allied to the Prostigmata, there is no trace of a

respiratory system.

Many of them are parasitic, others are free-living and feed on

Fie. 75.

House-mite, Glycyphagus domesticus,

x 50 (after Michael).

animal and vegetable refuse.
Tt is to this sub-order that the
mite (Sarcoptes scabier) which
is the cause of itch belongs.
The cheese mite (T'yroglyphus
siro) is perhaps the most fami-
liar of the non-parasitic forms.
Another species (Glycyphagus
domesticus) is often found in

_ houses. Drawings of these two
species are shown in Table-
case 26.

A taft of wool, with some of
the flesh still attached, showing
the scab caused by a Sarcoptid
mite (Psoroptes communis, var.
ovis), together with drawings
of the mite itself, is on view
in the North Hall.

Table-case
No. 26.

114 Guide to Arachnida.

SUB-ORDER VI.—VERMIFORMIA.

Table-case The Acari belonging to this sub-order are degenerate, parasitic

No. 26. forms without tracheae, and with the posterior portion of the
body produced into an annulated caudal prolongation. The third,
fourth, fifth, and sixth pairs of appendages are short and three-
jointed.

The sub-order includes the single family Demodicidae, the
members of which live in the sebaceous glands of the skin of man
and other mammals. <A drawing of Demodex caninus, a species
which gives rise to follicular mange in dogs, is exhibited in Table-
case 26. This mite is about one-eightieth of an inch in size.

Fia. 76. EG Ea ile
Demodex canmnus, ven- Ventral view of a gall-
tral view of female. mite, Hriophyes sil-
Greatly magnified vicola, x 135 (after
(after Canestrini). Canestrini).

SUB-ORDER VII.—TETRAPODA.

These mites are degenerate forms, which resemble the Vermi-
formia in being without tracheae and in having the body prolonged
and annulated. The legs of the first two pairs are long and
provided with the normal number of segments, but those of the
third and fourth pairs are absent.

To this sub-order belong the gall-mites, which form a single
family, Hriophyidae (Phytoptidae). They are of very small size and
are exclusively parasitic on plants of various kinds: many of them
give rise to pathological conditions resulting in scars, galls, or

Pycnogonida. es

other exerescences of the stem or leaves, but a number of

species are wandering forms, or live in the galls of other species.
A drawing of one of these mites (Hriophyes silvicola), which
produces galls on the leaves of the stone-bramble (Rubus saratilis),
is placed in Table-case 26, and models of some of the commoner
galls, and enlarged sketches of the mites which cause them, are
shown along the wall to the left of the Case. Drawings of the
black-currant mite (Hriophyes ribis) and of the plum mite
(EHriophyes prunc), together with specimens of the plants they
infest, showing the damage which they cause, are shown in the

North Hall.
Sub-class 2..-PYCNOGONIDA.

The Pycnogonida, Pantopoda, or Podosomata, are a small group
of marine animals, here treated as a sub-class of the Arachnida,

Proboscts
\ 1

Diagram of a Pycnogonid, Nymphon (Boreonymphon) robustwm.
Enlarged. [Table-case No. 26. |

although it should be mentioned that many zoologists refuse to
admit that they have any close affinity with that group of animals.

The body (Fig. 78) consists, as a rule, of a head-segment,
followed by three free somites and a small terminal lobe repre-
senting the abdomen or opisthosoma. Four pairs of very long
legs (1v.-vil.) are attached, the first to the head-segment, and the
others to the three free somites. In addition, the head-segment
may bear three pairs of appendages; the first pair (1.) are chelate
(or pincer-like), and overhang a tubular proboscis on which is the
opening of the mouth; the second pair (11.) are sensory palps,
placed at the sides of the proboscis; the third pair (111.), placed

I 2

Table-case

No. 26.

L16 Guide to Arachnida.

Table-case just behind the last, are used, in the male sex, for carrying the eggs,

No. 26.

and are known as “ oyigers.’’ One or other of the first three pairs,
or (in the female sex) all of them, may be absent in certain genera.

The apparent resemblance of a Pycnogonid to an Arachnid is
due chiefly to the four pairs of long and slender legs, and to the
chelate form of the first pair of appendages. The comparison,
however, is complicated by the fact that the Arachnida possess but
one pair of appendages, the pedipalps, between the chelicerae and
the first legs, while the Pyenogonida have two pairs, the palps
and the ovigers, in the same position. A further serious difficulty
in the way of comparison is
raised by the existence, in
Antarctic seas, of two genera,
Decolopoda (Fig. 79) and
Pentanymphon, which have
five, instead of four, pairs of
legs, and four free somites
behind the head.

The internal structure
presents many exceptional
features, which are illustrated
by the drawings exhibited
above the Table-case. The
food-canal sends long diver-
ticula into the appendages,
and the generative glands also
are partly situated in the legs
and open to the exterior by

pores on the second segments
Decode australis a tnlegel of some or all the pairs. A
Slightly reduced. [Table-case No. 26.) remarkable fact in the breed-
ing habits of these animals is

Eie. 79.

that the eggs are carried, after deposition, not by the female, but
by the male, attached in clusters to the third pair of appendages.
The Pyenogonida are all marine animals, ranging from shallow
water to depths of at least 2,000 fathoms. They are especially
abundant in the Arctic and Antarctic regions. The specimens ex-
hibited include Pycnogonwm littorale, which is common between tide-
marks on the British coasts ; Nymphon (Loreonymphon) robustum
(Fig. 78), a characteristic Arctic species ; two species of the deep-sea
genus Colossendeis, which includes the largest of the Pycnogonida;
and the ten-legged Pentanymphon and Decolopoda already alluded to.

_—_— = - ~~

Pentastomida. 117

APPENDIX TO ARACHNIDA.

PENTASTOMIDA.

The Pentastomida, or Linguatulida, represented in Wall- Wall-case
case 7 by Pentastomum arnillatum from an African python, N° f
and Linguatula taenioides from the nose of the dog, are always
parasitic, and have been so much modified by this habit that
there is little left to show their affinity to the Arachnida. The
segmentation of the body, and the hooks on either side of the
mouth, are the sole external indications of their relationships.

The third preparation, showing the young in the visceral mem-
branes of a mammal, forms an interesting link in the life-history

Hrie.-.80:

Pentastomum armillatum. (Natural size.)

of these creatures; it appears that the python gets its lung-
parasite from eating a small mammal; the parasite becomes
sexually mature in the lung of its new host, and the eggs from
the lung are coughed out, and are taken up by the mammal,
when in search of food.

The external ringing of the body does not correspond with any
internal segmentation ; the characteristic hooks are capable of
protrusion and retraction; the only sense-organs are some paired
papillae on the head; the sexes are separate, and the eggs are
considerably developed before they are laid.

Wall-case
(see plan
on p. 10).

118 Guide’ to Onychophora.

Class 4.—ONYCHOPHORA.

Tuis division of the Animal kingdom is represented by a number
of forms closely resembling one another in appearance and habits,
and for a long time known by the general name of Peripatus. In
recent years the differences between them have been accentuated
by systematists. Examples are shown of Peripatus from Jamaica,
of Peripatopsis from the Cape of Good Hope, and of Hoperipatus
from Malacca; while figures illustrative of the natural habit are
given of Peripatopsis capensis, of Hoperipatus viridimaculatus from
New Zealand, and Paraperipatus from New Britain. It will be
seen, therefore, that the distribution of this form is extremely wide,

Peripatus braziliensis. (Natural size ; from life.)

and, like other widely distributed forms, it gives indications of
being a very primitive type.

The history of the discovery of its affinities is one of the most
interesting pages in the history of Zoology. First discovered by
Guilding, it was, from its shape and habits, regarded as a slug;
later on, attention was directed to the fact that the body consisted
of a series of successive segments, and the question was hotly dis-
cussed as to whether it was more nearly allied to the rmged worms
or to the centipedes : against their alliance with the latter there was
the weighty objection that nearly all the muscles of Peripatus were
plain, and not banded. Up to the year 1873 no living specimen
had been examined by any anatomist; in that year, however,
during the voyage of H.M.S. “ Challenger,” H. N. Moseley, one of

Pertpatus. 119

the most gifted naturalists of his time, had the opportunity of Wall-case
dissecting freshly killed specimens at the Cape of Good Hope. (see a

When opened under water a glistening appearance revealed oo
the presence of air-tubes, such as are found among insects, spiders
and centipedes, and nowhere else in the animal kingdom; but,
whereas in these three groups the air-tubes (or trachexw) are
supported by a spiral coil of chitin which keeps them open after
preservation in spirit, those of Peripatus are not so supported.

Fortunately also this Peripatus was viviparous, and, as the
anatomical drawing in the case shows, a number of eges were
found in the oviduct ; these are in various stages of development :
following them out Moseley was able to see that the first of the
appendages are converted into mouth-organs. This is a character
which distinguishes the centipede from the ringed worm, and so far
settled the question of the relationship of Peripatus. But Moseley
did more than this, he showed that Peripatus belonged to that
division of the Arthropoda which is known as Tracheata, and
which consists of scorpions, centipedes, flies and their allies.
During the last quarter of a century much attention has been
paid to the Onychophora, of which more than 50 species are
now known.

Peripatus is to be found in moist and shady places. It avoids
light, and is nocturnal in its habits. On irritation, it shoots out
fine threads of a tenacious milky fluid, not unlike the threads of a
spider’s web. This fluid is sticky enough to hold fast flies. In
moving it never wriggles, but has a gait extremely like that of a
caterpillar.

There are a number of more or less minute characters by
which the species are distinguished from one another. The most
remarkable difference perhaps is in the characters of their eggs.
In the Neotropical species, represented here by P. juliformis, the
ege is minute, and almost entirely devoid of yolk. In the Cape
species (Peripatopsis capensis) the eggs are larger and there is
some yolk. In the eastern species (e.g., Hoperipatus horstv) the
egg is large, and there is a quantity of food-yolk. One at least of
the Australasian species lays eggs, which are hatched outside the
body. Thespecies vary further in the number of legs, and also in
the constancy or inconstancy of the number; that is to say, some
species have a definite number of legs, while others vary consider-
ably in the number that they possess.

The group is of great scientific interest as a clear link between
Arthropods and Polychaete worms.

Table-case
No. 27.

120 Guide to Myriopoda.

MYRIOPODA.

The classes which are included together under the name
Myriopoda are divided into two main divisions: The first of these
contains the forms in which the genital aperture is situated in the
anterior part of the body (Diplopoda, Pauropoda, and Symphyla).
The second division contains the Chilopoda, in which the genital
aperture is situated at the posterior end of the body near the anus,
as in the insects.

Owing to the importance attached to this character, some
authorities do not recognise the Myriopoda as a natural group.

Class 5.—DIPLOPODA (Millipedes).

The Diplopoda are terrestrial Arthropoda, which breathe
atmospheric air by means of tracheal tubes. The body-seg-
ments are numerous and, except at the anterior end of the
body, each bears two pairs of legs (whence the name of the
class), probably owing to the coalescence of adjacent segments in
the course of development. The genital orifice is situated in the
anterior part of the body between the second and third segments
of the body. The head bears a pair of antennae. In the
Chilognatha the mouth-parts consist of a pair of jointed
mandibles, and a single quadrate plate, the ‘ gnathochilariwm,”
probably representing two pairs of maxillae. In the Pselapho-
gnatha, however, the mandibles are followed by a_ pair of
maxillulae,a pair of maxillae, and a labium, the latter probably
representing a second pair of maxillae.

The Diplopoda are all plant feeders, and none of them are
venomous. On the other hand, many of them possess stink-
glands, placed along the sides of the body, which secrete an
offensively smelling fluid. With the exception of the Pselapho-
gnatha they are slow-moving forms. There are two sub-classes.

Sub-class I.—PSELAPHOGNATHA.

The members of this sub-class are small, soft-bodied forms, in
which the body is composed of eleven segments and _ bears
thirteen pairs of legs. The upper surface of the head and body-
segments is furnished with a number of flattened scale-like hairs,

ee

a
3
'
|

Diplopoda. ey

and large tufts of similar hairs project from the sides of each Table-case

segment; the last segment is furnished with a tuft of long hairs. NOs
The mouth-parts consist of paired mandibles,

li . | maxillulae and maxillae and a labium.

These curious little millipedes are widely

distributed, and live beneath stones or

the bark of trees. There is a single

family, Polyxenidac, with two genera; one

species (Polyxenus lagurus) oceurs in this

country.

Sub-class II.—CHILOGNATHA.

The body of the Chilognatha is’ hard and
strongly chitinized, and is not furnished
with tufts of scale-like hairs. The maxillae

Fic. 82. usually fuse to form a complicated gnatho-
Polyxenus lagurus, the chilarium,

English bristly milli- There are three orders of Chilognatha.
pede, x 12. ‘

Order 1.—Oniscomorpha.

The body is short and stout in the Oniscomorpha, and there
are eleven, twelve or thirteen dorsal plates, the last of them being
of large size. The copulatory feet of the male are situated on the
penultimate segment. The tracheal tubes are branched, and there
are no stink-glands.

In general appearance
the smaller species resemble
closely the ‘ wood - lice,”
which belong to the widely
different group of the Crus-
tacea Isopoda (see p. 43),
and, like them, are able to
roll themselves into a ball.

They are widely distributed, Fia. 83.
but are veryrare in America. Sphaerothervwm punctatum (slightly

The typical dark variety of enlarged).

Glomeris marginata, the

Pill-Millipede, occurs in Great Britain and Ireland. In Southern
Europe a large number of sub-species and varieties of Glomerts

122 Guide to Myriopoda.

Table-case have been distinguished by differences in colour. The tropical

No. 27.

forms (Sphaerotherium, Zephronia, etc.), occurring in South Africa,
Madagascar and South East Asia, are often of large size.

Order 2..-_Limacomorpha.

In the Limacomorpha the body tapers anteriorly and posteriorly
and the segments number from nineteen to twenty, the dorsal
plate of the last of them being of small size. The copulatory feet
are situated on the penultimate segment. The tracheae are
branched, and there are no stink-glands.

The small slug-like millipedes belonging to this sub-order occur
in Java, Sumatra, and South America. As yet only three or four
species are known; they form a single family, Glomeridesnudae,
with two genera, Glomeridesmus and Zephroniodesmus.

Order 3.— Helminthomorpha.

The form of the body varies greatly in the Helminthomorpha,
and the number of segments varies from nineteen to over a
hundred in the different forms. The auxihary copulatory organs
of the male are situated on the seventh, on the seventh and eighth,
or on the sixth, seventh and eighth segments. The tracheal tubes
are not branched, but tufted. There are five sub-orders.

SuB-ORDER I1.—LYSIOPETALOIDEA.

The body of these millipedes is slender and sub-cyiindrical,
and the number of segments is large and variable. They have a wide
distribution.

Sus-orpDER I1.—COLOBOGNATHA.,

The Colobognatha differ from the other sub-orders of Helmin-
thomorpha in that the mandibles and gnathochilarium are simplified,
the mouth-parts being more or less of a suctorial type. The
segments are numerous, and stink-glands are present. They are
found in the tropical or warmer temperate countries of the globe.
There are two families: Platydesmidae (Platydesmus, ete.), and
Siphonophoridae (Siphonophora, Polyzonium, ete.).

Sus-orRDER III.—CHORDEU MOIDEA.

In the Chordeumoidea there are always either thirty or thirty-
two body-segments, bearing symmetrically placed bristles. Stink-
glands are absent. The Chordeumoidea are chiefly Huropean and
North American forms. The sub-order is represented in this
country by two species, the better known being Atractosoma
polydesmoides.

Liplopoda, Pauropoda. 123

Sus-orDER IV.-—IULOIDEA.

The body is elongated and cylindrical in these millipedes, and Table-case
the number of segments differs greatly in the various forms. Stink- N°. 2%.

Fie. 84.

Tulus varius. Natural size. (After Koch.)

glands are present. In the male the seventh segment is limbless.
In the tropical regions some of the Tuloidea (of the families Spiro-
streptidae and Spirobolidae) are of large size, one or two species
reaching a length of over ten inches. There are numerous repre-
sentatives in temperate countries. A
number of species occur in this country,
and several of them are injurious to
vegetation.

Sus-oRDER V.—POLYDESMOIDEA.

In the millipedes belonging to this
sub-order the body is either long or short,
cylindrical or rather flattened above, and
is often furnished with keels: the number
of segments is constant, and is either
nineteen or twenty, the seventh segment
of the male being furnished with a single
pair of feet. The species which inhabit
temperate countries are of small size, but
the tropical species (Platyrrhachus, etc.)
are often of large size and beautifully
coloured. The sub-order is cosmopolitan Big. 85.
in distribution; there are several British Polydesmoid millipede,
species, which mostly belong to the Muzydesmus angulatus.

Slightly enlarged.
genera Polydesmus and Brachydesmus After Saussur
5 c gf f : (After Saussure.)

Class 6.—PAUROPODA.

The members of this class differ from the Diplopoda in having
branched antennae. They are all very minute animals, mostly
measuring less than one-twentieth of aninch. The body-segments

[24 Guide to Myriopoda.

Table-case are twelve in number and there are nine pairs of limbs. The

No. 27.

genital aperture is on the third segment.

The Pauropoda were first discovered’ by Lord Avebury (Sir
John Lubbock), who found two species in London in 1866. He
says that, “ Pauwropus huxleyi is a bustling, active, neat and cleanly
creature. It has, too, a look of cheerful intelligence, which forms
a great contrast to the dull stupidity of the Diplopods, or the
melancholy ferocity of most Chilopods.” They are found amongst
decaying leaves in damp earth, and other similar situations.
Owing to their small size and fragility of structure, and to their
retiring habits, they are still very incompletely known. They have

Fic. 86. Fie. 87.
Pauropus huxleyr, * 24. Scutigerella immaculata, x 8.
(After Lubbock.) (After Latzel.)

been found in Europe, tropical Asia, and North and South
America, and it is possible that they have a very wide distribution.
There are three families. Drawings of Pawropus and Hurypauropus,
to illustrate the morphology of the Pauropoda, are placed in
Table-case 27.

Class 7.—SYMPHYLA.

In the Symphyla the generative apertures are situated at the
anterior end of the body, as in the Diplopoda and Pauropoda.
The antennae are long, unbranched, and many-jointed. There are
fifteen or sixteen body-segments, twelve pairs of legs, and four
pairs of mouth-appendages,

——s

Symphyla, Chilopoda. Wp

These minute Myriopods have a wide distribution; they have Table-case
been found in Europe, India, Java, Sumatra, South Africa and No. 28.
America. A few species occur in this country. There is a single
family, Scolopendrellidae, with two genera, Scolopendrella and
Scutigerella.

Class 8._CHILOPODA (Centipedes).

In the Chilopoda the body consists of a number of similar
segments, and with the exception of the last, each of them is pro-
vided with a pair of appendages. The generative organs open upon
the penultimate segment, behind the legs of the last pair. The
anterior extremity is differentiated into a head which bears a
single pair of antenniform, many-jointed, pre-oral appendages. The
anterior four pairs of post-oral appendages are modified as jaws, the
first pair being the bi-segmented biting mandibles, the second pair
the biramous foliaceous maxillae, the third pair the leg-like palpi,
or ‘ palpognaths,” and the fourth pair the powerful biting poison-
jaw, or “toxicognaths.” The rest of the appendages are loco-
motor in function, and are tipped with a single claw; those of the
last pair, however, are sometimes modified in various ways in

| relation to sex or otherwise.

| The Chilopoda were formerly associated with the Diplopoda.
_ They differ, however, essentially from the Diplopoda, as well as from
the Pauropoda and Symphyla, in the position of the generative
orifices at the posterior extremity of the body, a character in which
they agree with the Hexapoda or Insects. They are often switt-
moving forms, and are carnivorous.

There are two sub-classes, Artiostigma and Anartiostigma.

Sub-class -ARTIOSTIGMA.

The tracheal tubes are retained in the Artiostigma, and
their orifices open upon the pleural area of more or fewer of the
segments. A dorsal plate (tergum) and a ventral plate (sternum)
are present on each of the leg-bearing segments ; and the number

of ventral plates never exceeds that of the dorsal plates. There
are four orders.

Order—Geophilomorpha.

Chilopoda in which the body is long and vermiform, consist-
ing of a large number of somites varying, according to the genus,
from about thirty-nine to over one hundred and forty. Hach

126 Guide to Myriopoda.

Table-case Somite, with the exception of the first and last, is furnished

No. 28.

with a single pair of tracheal spiracles. The antennae are
short, and consist of fourteen segments; eyes are always absent.
The tergal plate of the segment bearing the toxicognaths is
always distinct, generally large, and separates the bead-shield
from the tergal plate of the first leg-bearing
segment.

The young when hatched have the same
number of segments as the adult. Like all
centipedes, the Geophilomorpha have poison-
glands, but their jaws are too weak to pierce
the human skin. They live a subterranean
existence, and their food consists almost
entirely of earthworms. Two of the British
species (Linotaenia maritima and Schendyla
submarina), however, are marine in_ habit,
and are found under stones between tide-
marks. A number of Geophilids (including
several British species, as Linotaenia cras-
sipes, etc.) have been observed to exhibit the
phenomenon of phosphorescence. The phos-
phorescent fluid which they emit possesses
irritating properties, and is used for defensive
purposes, and also, it is believed, as a means

Hic. 88.

Geophilus longicornis ; rk
(slightly enlarged). of sexual attraction.

Order —Scolopendromorpha.

Chilopoda, in which the body is of medium length, and bears,
invariably, twenty-one or twenty-three pairs of legs. As arule the
stigmata are fewer than the legs, and are situated, roughly speak-
ing, upon alternate segments. The antennae are longish, and
never have fewer than seventeen, nor more than about thirty,
segments. The tergal plate of the segment bearing the poison-
jaws is suppressed, and the head-shield is in contact with the
tergal plate of the first leg-bearing segment.

The young, which are generally, perhaps always, born alive,
have the same number of segments as the adult.

Some of the tropical members of the Scolopendromorpha are of
large size, and are much dreaded on account of their venomous
bite. It is alleged, indeed, that the claws of the legs are poisonous
to a small extent, and that when one of these animals crawls over
the human skin, it leaves a track of inflammation behind it. Their

el

Chilopoda. 127

food consists of various insects, spiders, mice, or any living thing Table-case
that they are able to overpower. The largest known centipede er ee
(Scolopendra gigas), which is an inhabitant of the West Indies and

South America, sometimes reaches a length of almost a foot. The

genus Alipes, which is confined to tropical Africa, is remarkable

for the very peculiar structure of the posterior legs, which are
modified to form a_stridulatory
organ, whereby the animal emits
a hissing sound. Hthmostigmas
trigonopodus is the largest and
commonest of the tropical African
species of centipedes, and it is erent
also met with less frequently in
the more temperate parts of Africa.
Several of the species belonging
to this order are very widely dis-
tributed, and two of them (Scolo-
pendra morsitans and S. swbspi-
nipes), have been introduced, like
the common rat or cockroach, into
most of the seaport towns of the
world, but, unlike these animals,
they are unable to maintain them-
selves as far north as England.
This order includes only a single
British member (Cryptops hor-
tensis), which is not uncommon
in gardens,

Order—Craterostigmo-
morpha.

The dorsal plates number
twenty-one in this order, but there
are only fifteen pairs of legs, and
the stigmata are reduced in num- %¢elependra morsitans (after Koch).
ber as in the Lithobiomorpha.

There is only a single species (Craterostigmus tasmanianus),
which occurs in ‘Tasmania.

Fie. 89.

Order—Lithobiomorpha.

Chilopoda in which the body is short and furnished with only
fifteen pairs of legs, and six or seven pairs of stigmata arranged

128 — Guide to Myriopoda.

Table-case approximately upon alternate segments, the terga without stigmata

No. 28.

being greatly reduced in size.

The young, upon hatching, have only seven pairs of legs, the
remaining eight being added with successive moults.

The Lithobiomorpha are swift-footed centipedes, which live
under stones or fallen tree-trunks, and feed upon worms, insects,
etc. They do not attain to any great size.

There are about half-a-dozen British species of Lithobius ;

perhaps the commonest of them is
Inthobius forficatus.

Sub-class
ANARTIOSTIGMA.

The normal tracheal system is
replaced in the Anartiostigma by a
series of median dorsal pulmonary
sacs, furnished with tubes dipping

: into the pericardial space, and open-
~ ing each by a single stigma which
results from the upward migration

Ah j ff XY d and coalescence of the normal pair

of stigmata upon the first, third, fifth,

eighth, tenth, twelfth, and fourteenth

/ : segments. The remaining segments

/ do not bear stigmata, and their dorsal

plates are reduced or absent, that of

the seventh disappearing completely.

The antennae are very long and

\ filiform ; the legs, of which there are

_ fifteen pairs, as in the Lithobio-

Fic. 90. morpha, are also very long, and have

Scutigera (Cermatia) forceps (after the terminal Selguunres many-jounveds

Kingsley). The Scutigeridae (Fig. 90), the

only family of the Sub-class, reach

their greatest size in the tropics, and are quite unknown in north

temperate and Arctic countries of the world. Most of the

members of the order are of rather small size, but one or two of

the Oriental species (Scutigera longicornis, ete.) reach a length of

several inches. They live on insects, and are remarkable for

their extreme swiftness of foot. They also have a habit, when

pursued or seized, of dropping their legs. Hence it is exceedingly
difficult to capture undamaged specimens.

|

A.

ABDOMEN of Arachnida, 80;
of Crustacea, 13

Acanthephyridae, 51

Acanthogammarus, 46

Acari, 109

Acid-glands, 89

Acorn-shells, 33

Actinopus, 95

Adaptation to Environment
in Crustacea, 24

Aegina, 46 (fig.)

Aeglea, 63

Aegleidae, 63

Agelenidae, 92, 100

Albunea, 64 (fig.)

Albuneidae, 64.

Alcock, 59

Alima, 48

Alipes, 127

Alpheidae, 52

Amblypygi, 89

Amphipoda, 45

Anadiastothele, 93

Anartiostigma, 128

Anaspides, 13, 37 (fig.)

Andrews, 62

Anelasmocephalus, 108

Anepignathi, 108

Anomura, 59

Anostraca, 26

Antenna of Crustacea, 15

Antennule of Crustacea, 15

Anthracomarti, 107

Ant-like Spiders, 100, 102

Appendages of Crustacea,
15; of Arachnida, 80; of

Trilobita, 78; of Onycho- |

phora, 119
Apseudes, 40 (fig.)
Apus, 26 {fig.)
Arachnida, 9, 80
Arachnomorphae, 96
Arachnomysis, 39
Aranea, 97
Araneae, 91
Arcturidae, 43
Arcturus, 43, 44 (fig.)

| Arctus, 56

| Argas, 111
Argasinae, 111

| Argiopidae, 97

| Argulus, 30

| Argyroneta, 101
Arthrobranchia, 17

| Arthropoda, 9

| Artiostigma, 125

Asellota, 42

Asellus, 42

Astacidae, 55

Astacidea, 53

Astacoides, 56

Astacopsis, 55 (fig.), 56

Astacus, 55

Astigmata, 113

Asymmetry in Crustacea,
23

Atractosoma, 122

Atypidae, 96

| Atypus, 96 (fig.)

Auditory organ, of Crus-
tacea, 19

| Avebury, Lord, 124

Avicularia, 95

Aviculariidae, 94

153,

Balanus, 32 (fig.), 34
Barnacles, _ sessile,
stalked, 32
Basis, 15
Bathynomus, 41 (fig.), 42
Bdella, 113
Bdellidae, 113
Beetle-mites, 110
Belinurus, 82
Belisarvus, 85
Bird-eating Spiders, 94
Birgus, 60, 61 (fig.)

33;

Black-currant Mite, 115

Bopyrus, 44

Boreonymphon, 115 (fig), |
116

| Bothriuridae, 86
| Bothriwrus, 86
| Brachydesmus, 123

| Brachyura, 64.
Brain of Crustacea, 19
Branchiae of Crustacea, 17
Branchial cavity, 15; la-

mellae, 81

Branchiopoda, 2 25
Branchiostegite, 15
Branchiura, 30
Bristly Millipede, 121 (fig.)
Broteas, 87
Browne, 27
Butheolus, 85

| Buthidae, 87

| Buthus, 85 (fig.), 86, 87

G
| Caerostris, 98.
Calappa, 67 , 70
Calappidae, 67
| Callanassa, 59
| Calling Crab, 74
Calocalanus, 30 (fig.)
Calommata, '96
| Calymene, 78 (fig.)
Camarostome, 109
| Cambarus, 56
| Cancer, 72
| Cancridae, 72
Capitulum, 32
| Caprellidae, 24, 47
Caprellidea, 47
_Carapace of Crustacea, 13;
of Arachnida, 80
Carcinoscorpius, 82
Carcimus, 35, 44, 71
| Cardisoma, 74
| Caridea, 51
| Carpilius, 70
| Catometopa, 73
Catophragmus, 33
Caudal fork, 29
Centipedes, 125
| Centrurus, 86, 87
Cephalic shield, 77
Cephalothorax of Orus-
tacea, 14; of Arachnida, 80
Ceratiocaridae, 37
Cercophonius, 86

K

130

Cermatia, 128 (fig.)

Cervical groove, 15

Charontinae, 90

Cheese-mite, 113

Chelate, 17

Chelicerae, 81

Chelrfer, 105 (fig.), 106

Cheliferidae, 106

Cheliped, 17

Chelwra, 42, 47

Chelypus, 104

Chilobrachys, 91

Chilognatha, 121

Chilopoda, 125

Chitin, 21

Chordeumoidea, 122

Chthoniidae, 106

Cirri, 32

Cirripedia, 31

Cladocera, 27

Classification of Crustacea,
25; of Arachnida, 80; of
Acari, 109

Clubionidae, 99

Coco-nut Crab, 60, 61 (fig.)

Cocoon of Araneids, 92

Coenobita, 61

Coenobitidae, 61

Colobognatha, 122

Colossendeis, 116

Colulus, 96

Commensalism, 60

Conchostraca, 27

Copepoda, 29; parasitic, 30

Copulatory organ, 91, 106

Coronula, 34

Corystes, 73 (fig.)

Corystidae, 72

Courtship of Spiders, 101

Coxa of Crustacea, 15

Crabs, 64

Crab-spiders, 99

Crangon, 53

Crangonidae, 53

Craterostigmomorpha, 127

Craterostigmus, 127

Crawfish, Sea, 56

Crayfishes, 55; blind, 56;
Northern, 55; red-clawed,
55; Southern, 56 ; white-
clawed, 56

Cribellum, 96

Crustacea, 11

Cryptolithodes, 62

Cryptops, 127

Cryptostemma, 106 (fig.)

Cryptostemmatidae, 107

Cryptostigmata, 110

Ctenizidae, 95

Cumacea, 39

L[ndex.

Cyamidae, 47

Cyclometopa, 70

Cyclophthalmus, 85

Cymothoidae, 42

Cypris, 29 (fig.)

Cypris-stage of Cirripedes,
33

Cythereis, 29 (fig.)

1D).

Damon, 89 (fig.)

Daphnia, 27, 28 (fig.)

Darwin, 34, 92

Decapoda, 50

Decolopoda, 116 (fig.)

Delobranchia, 81

Demodex, 114 (fig.)

Demodicidae, 114

Desis, 101

Development, of Lobster,
20

Diastylis, 40 (fig.)

Digestive gland, of Crus-
tacea, 18

Digestive system, of Crus- |

tacea, 17
Diplopoda, 9, 120
Dipluridae, 94
Dispersal of young spiders,

92
Dorippidae, 68
Dromia, 65 (fig.)
Dromiacea, 65
Dromiidae, 65
Dwarf males, 31, 33
Dynomene, 66
Dynomenidae, 66
Dysderidae, 101

E.

Hbalia, 24, 68
Ecdysis, 21
Echidnocerus, 62
Edible Crab, 22, 72
Eggs of Lobster, 20
Embolobranchia, 84
Endopodite, 15
Hoperipatus, 118

| Hoscorpius, 85

EKpeiridae, 97
Hpevra, 97
Hiphebopus, 95
Epiblemum, 102 (fig.)
Epicaridea, 44
Epipodite, 16
Eresidae, 101
Hresus, 101
Hrichthus, 48

Eriophyes, 114 (fig.), 115
Eriophyidae, 114
Hryon, 59

Eryonidea, 58
Estheria, 27 (fig.)
Hthmostigmus, 127
Euarachnida, 81
Eucarida, 49
Huchaeta, 30
Eucopepoda, 30
Humunida, 68
Hupagurus, 60 (fig.)
Euphausiacea, 49
Hurydesmus, 123 (fig.)
EHurypauropus, 124
Kurypterines, 83
Hurypterus, 83 (fig.), 84
Huscorpius, 85, 87
Hurythenes, 46
Exopodite, 15
Exoskeleton, 12

Eye-stalks, 17

iE

False Scorpions, 104
False Spiders, 102

| Feaellidae, 106
| Feelers, 15, 81

Fiddler Crab, 74

Flabellifera, 42

Flagellum, 103

Flower-spiders, 99

Fossil, Crustacea, 38 ;
Pseudoscorpions, 105 ;
Scorpions, 85; Spiders,
93, 94

Fowl-tick, 111

Frog-Crab, 68

G.
Galathea, 63
Galatheidea, 63
Galea, 105
Galeodes, 1038 (fig.), 104
Galeodidae, 104
Gall-mites, 114
Gamasidae, 110
Gamasus, 110 (fig.)
Gammaridea, 45
Gammarus, 45 (fig.), 46

_Garypidae, 106

Gasteracantha, 97 (fig.), 98
Gastric mill, 17
Gelasimus, 74, 75 (fig.)
Geocarcinidae, 73
Geocarcinus, 74
Geophilomorpha, 125
Geophilus, 126 (fig.)

—__

—

Geralinura, 88

Giant Japanese Crab, 69
(fig.)

Gigantostraca, 83

Gills, of Crustacea, 16, 17

Glomeridesmidae, 122

Glomeridesmus, 122

Glomeris, 121
Glycyphagus, 113 (fig.)
Glyphaea, 58

_ Glyphaeidae, 58

Gnathobase, 16
Gnathochilarium, 120
Gnathophausia, 39 (fig.)
Gonoplacidae, 76
Gonoplax, 76
Gonyleptes, 107 (fig.)
Goose-barnacle, 31
32 (fig.)
Graeophonus, 90
Grapsidae, 74
Grapsus, 74
Grassi, 90
Green glands, 19

(fig.), |

H

Halacaridae, 112

Halicarcinus, 76 |

Harvest-bug, 112
Harvest-men, 107
Head of Crustacea, 14; of
Trilobita, 77
Heart of Crustacea, 18
Helminthomorpha, 122
Hemiaspis, 82
Hemictenodactyli, 105, 106
Hermit Crabs, 60 (fig.)
Heterophrynus, 90
Heteropoda, 99
Hexisopodidae, 104
Hexisopus, 104
Hibernation, 105
Hippaseae, 100
Hippidea, 64
Homaridae, 53
Homarus, 54
Homola, 66 (fig.)
Homolidae, 66
Homolodromiidae, 66
Hoplocarida, 47
House-mite, 113 (fig.)
House-spiders, 99, 100
Huenia, 68
Hyas, 24
Hydrachnidae, 112
Hymenosomidae, 76
Hyperiidea, 47
Hypochilus, 96

Index.

Ibla, 33

Idotea, 43

Insecta, 9

Internal Anatomy, of Lob-
ster, 17, 18 (fig.)

Iphinoé, 39

lsometrus, 85, 87

Isopoda, 41; parasitic, 42,
44

Itch-mite, 113 (fig.)
Tuloidea, 123
Zulus, 123 (fig.)

| Turus, 87

Ixodidae, 110
Txodinae, 111

J

Joint, 13
Jumping Spiders, 101

=

K

Kaempferia, 69 (fig.
King-crabs, 11, 81,

)
82, (fig.)
Koenema, 90 (fig.)

L

Lamina, 105

Land-crabs, 61, 73

Laniatores, 107

Larve of Lobster, 21; of
Stomatopoda, 48; of
Loricata, 58

Laterigrade-spiders, 99

| Latrevilia, 66
| Latreilliidae, 66

Lathrodectus, 98 (fig.)
Leander, 44, 53 (fig.)

| Legs of Crustacea, 15, 17
Lepas, 31 (fig.), 32 (fig.)

Leptodora, 28 °
Leptomysis, 39
Leuweifer, 51
Leucosiidae, 67
Ligia, 43

Limacomorpha, 122
_ Limnoria, 42 (fig.)
| Limulus, 82

Linguatula, 117
Linotaenia, 126
Liphistius, 93 (fig.)

| Lithobiomorpha, 127

Lithobius, 128
Lithodes, 62 (fig.)
Lithodidae, 60, 62

131

Lobster, as type of Crus-
tacea, 12; Common, 13
(fig.), 54; Murray River,
56; Norway, 54 (fig.) ;
Spiny, 56, 57 (fig.)

Lophogastridae, 39

Loricata, 56

Loricula, 33

Lubbock, 124

Lung-books, 84

Lung-sacs, 91, 93, 94, 96

Lycosa, 100

Lycosidae, 92, 100

Lysvoerichthus, 48

Lysiopetaloidea, 122

Lysvosquilla, 48

M.

Macrocheira, 69 (fig.)

Macromysis, 39

Macrophthalmus,
76 (fig.)

Macropodia, 24, 68

Macrura, 51

Mana, 24, 69

Maiidae, 68

Malacostraca, 36

Malleoti, 103

Mandible of Crustacea, 15,
16

Manges, in dogs, 114

Margaropus, 111 (fig.)

Marine mites, 112; spider,
101

Mastigoproctus, 88

Matuta, 67

Maxilla of Crustacea, 15,

72, 15,

16

Maxilliped of Crustacea,
15, 16

Maxillula of Crustacea, 15,
16

Meganyctiphanes, 49 (fig.)

Mesosoma, 80

Mesothelae, 93

Metasoma, 80

Metastigmata, 110

Millipedes, 120

Mimicry, 100, 102

Misumena, 99 (fig.)

Mites, 109

Moseley, 118

Moulting of Arachnida, 105;
of Crustacea, 21

| Munida, 63 (fig.)

Mygalomorphae, 94

| Myodocopa, 29

Myriopoda, 120

132

Myrmarachne, 102
Mysidacea, 38
Mysis, 38 (fig.)

N.

Nauplius, 33

Nebalia, 36 (fig.)

Nematocarcinidae, 51

Nematocarcinus, 52 (fig.)

Nematoscelis, 49

Nephila, 97

Nephrops, 54 (fig.)

Nephropsidea, 55

Neptunus, 71

Nervous system of Crus-
tacea, 19

Northern Stone-Crab, 62

Notaspis, 110

Notostigmata, 109

Notostraca, 26

Nymphon, 116

O.

Obisiidae, 106
Obisiwm, 105:
Ocypoda, 74
Ocypodidae, 74
Ogygia, 78 (fig.)
Oniscoidea, 43
Oniscomorpha, 121
Onychophora, 9, 118
Opercular plates, 33
Operculata, 33
Opilioacaridae, 109
Opilioacarus, 109
Opiliones, 107
Opisthophthalmus, 86
Opisthosoma, 80
Opisthothelae, 94:
Orb-webs, 97
Orchestia, 45
Oribatidae, 110
Ornithodoros, 111
Ostracoda, 28
Oviger, 116
Oxyrhyncha, 24, 68
Oxystomata, 66

iP:

Paguridae, 60
Paguridea, 60
Paguropsis, 60
Pagurus, 61
Palaemon, 53
Palaemonidae, 53
Palamnaeus, 85
Palinuridae, 56

Index.

Palinurus, 56, 57 (fig.)
Palp of Arachnida, 81; of
Crustacea, 17
Palpatores, 108
Palpigradi, 90
Palpognaths, 125
Panctenodactyli, 105, 106
Pandalidae, 52
Pandalus, 52
Pandinidae, 86
Pandinus, 85, 86
Pantopoda, 115
Panulirus, 56
Parapervpatus, 118
Parasites, modifications
caused by, 23
Parilia, 67
Paromola, 66
Parthenope, 70
Parthenopidae, 70,
Pauropoda, 9, 123
Pawropus, 124 (fig.)
Pedipalpi, 87
Pedunculata, 32
Penaeidea, 51
Penaeus, 50 (fig.), 51
Pennella, 30
Pentanymphon, 116
Pentastomum, 117 (fig.)
Peracarida, 38
Pericardiam of Crustacea,
18
Pervpatopsis, 118
Peripatus, 118 (fig.)
Phalangiidae, 108
Phalangivwm, 108
Philodrominae, 99
Philomedes, 29 (fig.)
Phosphorescence,
59, 126
Phreatoicidea, 42
Phronima, 47
Phyllocarida, 36
Phyllopoda, 25
Phyllosoma, 58 (fig.)
Phytoptidae, 114
Pill-Millipede, 121
Pinnaxodes, 75
Pinnotheridae, 75
Planes, 74
Plankton, 29
Platydesmidae, 122
Platydesmus, 122
Platyonychus, 72
Platyrrhachus, 123
Pleopod, 15
Pleurobranchia, 17
Pleuron, 14
Plum mite, 115
Podobranchia, 17

49, 51,

| Podocopa, 29

| Podogona, 106
Podophthalmus, 72 (fig.), 75
Podosomata, 115
Poison-glands, 86, 91
Poison-jaws, 125

| Poison of spiders, 98, 100

Poliochera, 107

Pollacupes, 32

Polycheles, 59 (fig.)

Polydesmoidea, 123

Polydesmus, 123

Polyxenidae, 121

Polyxenus, 121 (fig.)

Polyzoniwm, 122

Porcelain Crab, 64

Porcellana, 64

Porcellanidae, 64

Porcellio, 44 (fig.)

Portunidae, 70

Portwnon, 44

Portunus, 71

Potamon, 72

Potamonidae, 72

Praeanaspides, 37 (fig.), 38

Praegenital somite, 81, 105

Prawn, 44, 51; common,
53 (fig.); Dublin, 55;
River-, 53.

Prosoma, 80 —

Prosopon, 66

Prosoponidae, 66

Prostigmata, 111

Protolycosa, 93

Protopodite, 15

Protective resemblance in
Arachnida, 98, 99; in
Crustacea, 24

Psalmopoeus, 94

Pselaphognatha, 120

Pseudidiops, 95

Pseudocarcinus, 23, 70, T1
(i) a

Pseudoscorpiones, 104

Psoroptes, 113

Pterygotus, 84.

Pulmonary sacs, 91, 93, 94,
96, 128

Pyecnogonida, 115

Pycnogonum, 116

Pygidium, 78

Rh.

Rania, 68
Raninidae, 68
Respiratory system
Arachnids, 80
Rhagodes, 104
Rhizocephala, 35

of

————

River-Crabs, 72

Robber-Crab, 61 (fig.)

Rostrum of Acari,
of Crustacea, 13

Gs) 2

S.

Sacculina, 23, 35 (fig.)

Salticidae, 101

Sand-Crabs, 66

Sandhopper, 45

Sarcoptes, 113 (fig.)

Scalpellum, 33

Sclerocrangon, 53

Scolopendra, 127 (fig.)

Scolopendrellidae, 125

Scolopendromorpha, 126

Scorpiones, 84

Schendyla, 126

Schizomus, 89

Schizopoda, 49

Scutigera, 128 (fig.)

Scutigerella, 124 (fig.), 125

Scutigeridae, 128

Scutum, 33

Scyllaridae, 56

Scyllaridea, 56

Scyllarus, 56

Scytodes, 91

Sea-spiders, 11

*Segestria, 101

Segment, 13

Seothyra, 101

Serrula, 105

Sesarma, 74

Sexual differences of Crus-
tacea, 19

Shore Crab, 22 (fig.), 35, 44,
71

Shorehopper, 45

Shrimp, 51; Arctic, 53;
common, 53; pink, 52

Sicarlidae, 91

Sicarius, 91

Silk-glands, 105

Siphonophora, 122

Siphonophoridae, 122

Sironidae, 108

Slaters, 43

Snares, 97

Social Spiders, 101

Solifugae, 102

Solpuga, 104

Solpugidae, 104

Somite, 12

Spawning of Lobster, 20

Sperm receptacle, 20

Sphaeromidae, 42

Sphaerotherium, 121 (fig.)

Spiders, 91

Index.

Spider-Crabs, 68
Spinnerets, 91, 93, 94, 96
Spinning-mites, 112
Spirillosis, 111
Spirobolidae, 123
Spirostreptidae, 123
Squilla, 47, 48 (fig.)
Stegocephalus, 46
Stegodyphus, 101
Stenopidea, 51
Stenopus, 51
Sternum of Crustacea, 14;
of Trilobita, 78
Stink-glands, 107, 120
Stomatopoda, 47
Stone-Crab, Northern,
62 (fig.)
Streptocephalus, 26
Stridulatory organs,
127; ridges, 103
Stylocellus, 108 (fig.)
Stylonurus, 84
Swimmerets, 13
Swimming Crabs, 70
Symphyla, 9, 124
Syncarida, 37

91,

ab

Tachypleus, 82
Tail, 87
Tail-fan, 51
Talitrus, 45
Tanaidacea, 40
Tarantula, 100
Tarantulidae, 90
Tarsal comb, 98 (fig.)
Tartarides, 89
Tasmanian Crab, 23,71 (fig.)
Tegenaria, 100
Telson, 13
Tergum, of Trilobita, 78; of
Crustacea, 14; of Cirri-
pedia, 34
Testis of Crustacea, 19
Tetranychinae, 112
Tetranychus, 112
Tetrapoda, 114
Texas fever, 111
Thalassina, 59
Thalassinidea, 59
Thelphusa, 72
Thelphusidae, 72
Thelyphonus, 88 (fig.)
Theraphosa, 94
Theridiidae, 92, 98
Theridion, 98, (fig.)
Thomisidae, 99
Thompson, 31
Thoracica, 32

133

Thorax of Crustacea, 14

Ticks, 109, 110

Tick-fever, 111

Toxicognaths, 125

Tracheal tubes, 43, 91, 96,
119, 120, 121, 122, 125

Trap-door nests, 95, 100;
spiders, 95

Triaenonychidae, 108

Triarthrus, 77 (fig.), 79

Trilobita, 9, 77

Trithyreus, 89

Trogulidae, 108

Trogulus, 108

Trombidiidae, 112

Trombidiwm, 112

Tubrieinella, 34

Turrilepas, 33

Tyroglyphus, 113

U
Uca, 74
Urodacus, 86
Uropod, 15
Uroptychidae, 63
Uropygi, 87
Urotricha, 87

Vv

Valvifera, 42
Varuna, 74
Vejovidae, 86
Vejovis, 87
Vermiformia, 114

W

Waddington, 21
Water-fleas, 27
Water-mites, 112
Water-spiders, 101
Webs, 97

Whales, Cirripedes on, 34
Whale-lice, 47
Whip-scorpions, 87
Wolf-spiders, 100
Woodlice, 43
Wood-Mason, 91

xX
Xanthidae, 70
Xantho, 70
Xenesthis, 94
Xiphosura, 11, 81
Aiphosura, 82 (fig.)

Z

Zozymus, 70
Zephronia, 122
Zephroniodesmus, 122

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