GUIDE TO THE CRUSTACEA, ARACIIMDA. ONYCHOPHORA and MYRIOPODA EXHIBITED IX THE DEPARTMENT OF ZOOLOGY, BRITISH MUSEUM (NATURAL HISTORY), CROMWELL ROAD, LONDON, . S.W. WITH 90 ILLUSTRATIONS LONDON : PRINTED BY ORDER OF THE TRUSTEES OF THE BRITISH MUSEUM. 1910. [PRICE ONE SHILLING.] ti - III 1 1 II I II Hill I I III ■ I 22102035668 . Med K5680 GUIDE TO THE CRUSTACEA, ARACHNIDA, ONYCHOPHORA and MYRIOPODA EXHIBITED IN THE DEPARTMENT OF ZOOLOGY BRITISH MUSEUM (NATURAL HISTORY), CROMWELL ROAD, LONDON, S.W. LONDON : PRINTED BY ORDER OF THE TRUSTEES OF THE BRITISH MUSEUM. 1910. ( All rights reserved.) u LONDON : PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, DUKE STREET, STAMFORD STREET, S.E., AND GREAT WINDMILL STREET, W. WELLCOfv 3TITUTE LIBRARY Coll. welMOmec Cal! No. n PREFACE. This 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 Grabs ; 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. Caiman, that on the Arachnida and Myriopoda by Mr. A. S. 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. Caiman’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 Museum (Natural History), Cromwell Road, London, S.W. February , 1910. Digitized by the Internet Archive in 2016 https://archive.org/details/b28128060 TABLE OF CONTENTS. PAGE Definition and Subdivisions of Arthropoda .... 9 Plan of the Gallery ........ 10 Class 1.— CRUSTACEA ll Parasitism and Adaptations to Environment .... 23 Classification of Crustacea ....... 25 Sub-Class— BRANCHIOPODA 25 Order — Phyllopoda ...... 25 Sub -Order — Anostraca ..... 26 ,, Notostraca ..... 26 „ CONCHOSTRACA ..... 27 Order — Cladocera ....... 27 Sub-Class— OSTRACODA 28 „ COPEPODA 29 Order — Eucopepoda ...... 30 ,, Branchiura . . . . . . 30 Sub-Class— CIRRIPEDIA 31 Order — Thoracica ....... 32 Sub-Order — Pedunculata ..... 32 ,, Operculata ..... 33 Order — Rhizocephala ...... 35 Sub-Class— MALACOSTRACA 36 Series— LEPTOSTRACA 36 Division— Phyllocaeida 36 Series— EUMALACOSTRACA 36 Division — Syncarida .37 ,, Peracarida ...... 38 Order — Mysidacea ....... 38 ,, Cumacea ....... 39 ,, Tanaidacea ...... 40 ,, ISOPODA ....... 41 6 Table of Contents. PAGE Sub-Order — Asellota ...... 42 ,, Phreatoicidea ..... 42 ,, Flabellifera ..... 42 ,, Valvifera ..... 42 ,, Oniscoidea ..... 43 „ Epicaridea ..... 44 Order — Amphipoda ...... 45 Sub -Order — Gammaridea ..... 45 ,, Hyperiidea ..... 47 ,, Caprellidea ..... 47 Division— Hoplocarida 47 Order — Stomatopoda ...... 47 Division — Eucarida ...... 49 Order — Euphausiacea ...... 49 ,, Decapoda ....... 50 Sub-Order — Macrura ...... 51 Tribe — Penaeidea . . . . . . 51 ,, Stenopidea ...... 51 ,, Caridea ...... 51 ,, Astacidea (Nephropsidea) ... 53 ,, Loricata (Scyllaridea) .... 56 ,, Eryonidea ...... 58 ,, Thalassinidea ..... 59 Sub-Order — Anomura ...... 59 Tribe — Paguridea ...... 60 ,, Galatheidea ..... 63 „ Hippidea ...... 64 Sub -Order — Brachyura ..... 64 Tribe — Dromiacea ...... 65 ,, Oxystomata ...... 66 ,, OxYRHYNCHA ...... 68 ,, Cyclometopa ..... 70 ,, Catometopa ...... 73 Class 2.— TEILOBITA ... 77 Class 3. — ARACHNIDA ... 80 Sub-Class— EUARACHNIDA 81 Division — Belobranchia ..... 81 Order — Xiphosura ....... 81 „ Gigantostraca ...... 83 Division — Embolobranchia ..... 84 Order — Scorpiones ....... 84 ,, Pedipalpi ....... 87 Table of Contents . 7 PAGE Sub-Order — Uropygi ...... 87 Tribe — Urotricha ...... 87 „ Tartarides . . . . . 89 Sub-Order — Amblypygi ..... 89 Order — Palpigradi ....... 90 ,, Araneae ....... 91 Sub-Order — Mesothelae ..... 93 ,, Opisthothelae ..... 94 Tribe — Mygalomorphae ..... 94 ,, Arachnomorphae ..... 96 Order — Solifugae . . . . .102 ,, Pseudoscorpiones ..... 104 Sub-Order — Panctenodactyli .... 106 ,, Hemictenodactyli .... 106 Order — Podogona ....... 106 ,, Opiliones ....... 107 Sub-Order— Laniatores ..... 107 ,, Palpatores ..... 108 ,, Anepignathi ..... 108 Order — Acari ....... 109 Sub-Order — Notostigmata ..... 109 ,, Cryptostigmata. . . . .110 ,, Metastigmata . . . .110 „ Prostigmata . . . . .111 ,, Astigmata . . . . .118 „ Vermiformia ..... 114 ,, Tetrapoda . . . . .114 Sub-Class'— PYCNOGONIDA (PANTOPODA) ... 115 (Appendix to Aracknida) Pentastomida . . . .117 Class 4.— ONYCHOPHORA . . . 118 Class 5.— DIPLOPODA . . . 120 Sub-Class— PSELAPHOGNATHA 120 „ CHILOGNATHA .121 Order — Oniscomorpha ..... 121 ,, Limacomorpha ...... 122 ,, Helminthomorpha .... 122 Sub-Order — Lysiopetaloidea .... 122 ,, COLOBOGNATHA . . . . .122 ,, Chordeumoidea .... 122 ,, IlJLOIDEA ...... 123 ,, POLYDESMOIDEA ..... 123 8 Table of Contents. PAGE Class 6.— PAUROPODA ... 123 Class 7.— SYMPHYLA . 124 Class 8.— CHILOPODA ... 125 Sub-Class— ARTIOSTIGMA 125 Order — Geophilomorpha ...... 125 ,, SCOLOPENDROMORPHA ..... 126 ,, Craterostigmomorpha ..... 127 ,, Lithobiomorpha ...... 127 Sub-Class— ANARTIOSTIGMA 128 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, etc.). ,, 2. — Trilobita. ,, 3. — Arachnida (Spiders, Scorpions, etc., with Appendix, Pentastomida). ,, 4. — Onychophora (Peripatus). ,, 5. — Diplopoda (Millipedes). ,, 6. — Pauropoda. ,, 7. — Symphyla. ,, 8. — Chilopoda (Centipedes). ,, 9.— Insecta (Moths, Plies, Beetles, etc.). 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. ^ Myriopoda. Onychophora. West Entrance. East Entrance. Chilopoda. 28 Pauropoda. Symphyla. 27 Diplopoda. 25 Opiliones. Acari. * 26 Acari. Pycnogonida. Pseudo- Q Podogona. scorpiones Solifugae. 24 M Araneae. 23 21 22 Pedipalpi. Palpigradi. w Araneae. O Scorpiones. Scorpiones. Gigantostraca. 20 P 19 17 c 18 Trilobita. si' Xiphosura. Eurypterus. Brachyura. Brachyura. 16 15 13 14 Brachyura. Brachyura. Brachyura. Anomura. <1 Macrura. 12 P 11 9 O 10 Macrura. <3 Macrura. Euphausiacea. Stomatopoda. TJ1 Amphipoda. 8 P 7 5 6 Lower Malacostraca. o Tanaidacea. Isopoda. Cirripedia. 4 Cirripedia. 3 1 Branchiopoda. Ostracoda. 2 Copepoda. I I South Entrance. Plan of South Half of “Insect Gallery,” showing position of cases OCCUPIED BY GROUPS DEALT WITH IN THIS GUIDE. Definition of Crustacea. 11 Class i. — 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 12 Guide to Crustacea. Wall- cases Nos. 1- month and at least three pairs of jaw-like appendages behind the month, 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 haying 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 3 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- Crust acea and other Arthropoda has led to the conclusion that g 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 The Common Lobster (Homarus gammarus) . Female, from the side. [Wall-case No. 1.] f 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 14 Guide to Crustacea. Wall- cases Nos. 1-3. 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- derstood by examining one of the separated abdominal somites of the 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 Fig. 2. One of the abdominal somites of the lobster, with its appendages, separated and viewed from in front. [Wall-case No. 1.] Lobster — A ppendoges . 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 NosS1-3 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 lie 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. Each of these consists (Eig. 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 (Eig. 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 16 Guide to Crustacea. Wall- cases Nos. 1-i 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-parfcs 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 be recognised in it, but the endopodite is shorter than the exopodite and has only two seg- 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 maxilla ( 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 maxillula ( first maxilla i) 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 Third maxilliped of Lobster. [Wall-case No. 1.] L obster — A ppen dages , A natomy. 17 with its gnathobase, and a small “palp” of three segments Wall- representing the rest of the protopodite with the endopodite. NosT] 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 “ gastric mill ” which acts as a gizzard in grinding up the food. c 18 Guide to Crustacea . Wall- cases Nos. 1 -i It is divided into two chambers, a larger one in front, the “ cardiac chamber,” which serves as a kind of crop, and a smaller “ pyloric 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 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 L obster — 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 g 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, a 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.— Two 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 20 Guide to Crustacea . Wall- the under surface of the thorax, between the last two pairs of legs, NosT 1-3 a curi°us 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. Fig. 5. 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 21 L obster — Development, Moulting. adult animal. An enlarged drawing of this stage is hung in Wall- Wall-case No. 2. The most important differences from the adult g 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. At a 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 cast 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. EL 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 G uide to Crustacea. Wall- cases Nos. 1-i Fig. 6. Series of cast shells obtained from a single individual of the Shore-Crab ( Carcinus maenas ) kept in an aquarium. The carapace of the largest is about inches wide. [Wall-Case No. 3.] 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 from a single individual of the Shore-Crab (Eig. 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 cast shells, 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 a marketable size. The younger series begins with a specimen of about -fths 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 4£ inches in length. The second series begins with a specimen Asymmetry , Effect of Parasites. *23 of about 4| inches long, obtained on 16th September, 1901. Wall- Between that date and 31st July, 1909, when the lobster died, it ^ses-, 0 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 “ crushing- claw.” The other is more hghtly 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 (Pseudocar cinus gig as) , 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 PABASITES. 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 24 Guide to Crustacea. Wall- cases Nos. 1-f Wall- cases Nos. 1— ; 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 he 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 Ebalia (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 Eyas 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. 25 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 . . „ OSTRACODA . . . „ COPEPODA „ CIRRIPEDIA . . . „ MALACOSTRACA. Series Leptostraca. Division Phyllocarida Series Eumalacostraca. Division Syncarida . Peracarida Hoplocarida Eucarida . Order Phyllopoda. ,, Cladocera. C ,, Myodocopa. I ,, Podocopa. ( ,, Eucopepoda. Branchiura. Thoracica. Acrothoracica. Ascothoracica. Apoda. Rhizocephala. Order Nebaliacea. Order Anaspidacea. Mysidacea. Cumacea. Tanaidacea. Isopoda. Amphipoda. Stomatopoda. ( -7, Euphausiacea. | ,, Decapoda. 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, No‘ 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 maybe 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 26 Guide to Crustacea. Table-case primitive characters. In the large number of the somites and the N°. 1. 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. Fig. 7. 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 Notostraca 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 B ranchiopoda. 27 pools and ditches in many parts of Europe, but it is very uncertain in its occurrence, and it may suddenly reappear in numbers after 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. E. 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 Conchostkaca have the body enclosed in a bivalved shell, which resembles very closely the shells of some Molluscs. The genus Estheria (Fig. 8), of which speci- mens are exhibited, is of interest on account of its geological antiquity ; fossils referred to the genus occur in rocks of the Devonian period. Fig. 8. Estheria melitensis (slightly en- larged). [Table-case No. 1.] 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 Table-case No. 1. 28 Guide to Crustacea. Table-case No. 1. (Fig. 9). Leptodora ldndtii is the largest species of the Order. It 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. 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 No' 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, n) 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. Fig. 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; ci., 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 Muller.) Sub-class III. — COPEPODA. There are, at most, ten free somites behind the head. The Table-case carapace is reduced or absent. The first thoracic limbs form No- 2- 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 30 Guide to Crustacea . Table-case important part in the economy of nature than any other No. 2. 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 Eucopedoda (Eig. 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 Euchaeta norvegica, of which specimens are exhibited. The enlarged drawings show the brilliant colours of some pelagic species. Fig. 11. Caloccilanus 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 Branchiura includes a small number of fish- parasites whose exact relations tor 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- writer 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 Table- the anterior part of the head-region, and having the body generally 4 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 Fig. 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-ciass may be divided into five Orders, but three of these comprise only a few imperfectly-known forms which cannot be exhibited here. 32 Guide to Crustacea . Order 1. — Thoracica. Table-case 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 Pedunculata (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 anatifcra (Fig. 12), are exhibited showing the external appearance with the 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 ; l., lateral; r. + r.l., rostrum and rostro-lateral fused together ; sc., scutum ; t., 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. 13a) 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 which pass gradually into the small scales covering the peduncle. 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 Ibla. 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 Nauplii 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 Operculata (Fig. 13b), 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. In a preparation of Gatophragmus polymerus here exhibited, names are attached to those parts of the shell which are found (though often reduced iu number by coalescence) in all the typical Operculata, the “ scutum ” D Table-case No. 3. 34 Guide to Crustacea. Table-case No. 3. Table-case No. 4. and “ tergum ” forming the movable lid or “ operculum,” while the 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 samq 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 .” Cirripedia. 35 Order 2. Rhizocephala. The Rhizocephala are parasites living on other Crustacea, and Table-case they offer one of the most striking examples of the degradation in No- 4- 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, Fig. 14. Sacculina carcini 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 carcini , of which a specimen is exhibited (Fig. 14), is found on the common shore-crab ( Carcinus mamas) 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 Guide to Crustacea. 36 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. Leptostraca (Abdomen of seven somites). Division 1. Phyllocarida. Series 2. Eumalacostraca (Abdomen of six somites). Division 2. Syncarida. ,, 3. Peracarida ,, 4. Hoplocarida. ,, 5. Eucarida. Fig. 15. Nebalia bipes, female, from the side (enlarged), a.', Antennule; a.", antenna; ab.'-ab.*, the abdominal limbs ; ad., the adductor muscle joining the two valves of the shell; /., the caudal fork ; p., palp of maxillula ; r., rostral plate ; t., 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. Nebalia bipes, Malacostraca — 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 No- of a living Nebalia is hung in Wall-case No. 4. It is probable that the fossil forms known as the CeratiocaricLae, 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. 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:] 38 Guide to Crustacea. Table-case No. 5. This division includes, among living Crustacea, a small number 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. ,, 3. Tanaidacea. ,, 4. Isopoda. ,, 5. Ajnphipoda. 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. P eracarida — Mysidacea , Cumacea. 39 The eyes, when present, are stalked and movable. There are Table- swimming branches (exopodites) on the thoracic legs. 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 leuckarti 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 calcardta from the “ Challenger ” expedition is exhibited, and alongside of it is placed Gnathophausia willemoesii, female, from the side, one-half natural size. gr., a 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- lemoesii (Big. 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 Iphinoe trispinosa here 40 Guide to Crustacea. Table-case shown being perhaps larger than the average, but in Arctic seas, No- where they are especially abundant, they often attain a much greater size, as is shown by the specimen of Diastylis goodsiri (Fig. 20) from the Kara Sea. Diastylis goodsiri , female, from the side, enlarged, a.', antennnle ; Z.1-?.5, the five pairs of walking-legs; m., brood-ponch ; ps., “ pseudo-rostrum,” formed by lateral plates of the carapace ; t.. telson ; ur., nropods. (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 cavity within which lies ex. a Fig. 21. Apseudes spinosus, female, from the side, enlarged, ex., vestiges of exopodites on second and third thoracic limbs ; oc., the small and immovable eye- stalks ; sc., scale or exopodite of antenna ; ur., nropod. (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, ex.). The eyes, when present, are set on small and immovable stalks (Fig. 21, oc.). Peracarida — Tcinaidcicea , Isopoda. 41 The Tanaidacea, which are all marine, and generally of very Table-case small size, are of great interest as preserving, along with the No‘ 6‘ Cnmacea, 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 Fig. 22. Bathynomus giganteus, about one-half natural size. (From Lankester’s “ Treatise on Zoology,” after Milne-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. 42 Guide to Crustacea. Table-case No. 6. This is a very large and varied group, comprising numerous families which are grouped under six Sub-orders. In the Sub-order Asellota 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 Plabellifera 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 being hermaphrodite (like the Oirripedia), each animal being at first a male and afterwards a female. This family includes the giant of the Order, the deep-sea Bathynomus giganteus (Fig. 22), which some- times reaches an even greater size than -the Limnoria liqnorum, • ^ -t i much enlarged. specimen exhibited. (After Sars.) A contrast in point of size is provided by [Table-case No. 6.] 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 havoc 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 Valvifera 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 P 'eracarida—1 sopoda . 43 includes the species of Iclotea common on the British coasts, one Table- of which is shown in a coloured drawing hung in Wall-case No. 6. No- 6* The family Arcturidcce 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 Oniscoidea comprises the familar “ Woodlice ” Fig. 24. Piece of timber from Hyde pier, showing damage caused by Limnoria and Chelura. [Wall-case No. 4.] or “ Slaters ” so common 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 in 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. Fig. 25. 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 Epicaridea are all parasitic on other Crustacea, and their structure presents, in the 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 sence in the gill-chamber of the parasite Bopyrus squillarum. The female of the parasite, taken out of the gill-chamber, is shown alongside. The male, in this species, is 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 drawings of Portunion maenadis, a parasite of the common Shore-crab, Carcinus mamas. The figure on the right carapace, a swelling due to the pre- Porcellio scaber, female, dorsal view, enlarged. (From Lankester’s “ Treatise on Zoology,” after Sars.) Peracarida — A mphipoda. 45 shows the parasite in situ in the shell of the crab. The yellow mass is the greatly developed brood-pouch, which is distended 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 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 ; cx, coxal plate (the expanded first segment of the leg; gn, the two pairs of “ gnatho- pods ” (prehensile legs) ; pip'", abdominal appendage of third pair ; prp', prp", first and second peraeopods or walking-legs ; t, telson ; ur, 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. 6. Table-case No. 7. 46 Guide to Crustacea. Tablc-i No. 7. 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 Talitrus is stated to be more common on sandy beaches, while Orchestia is often found among rocks. More typical representatives of the Gammaridea, however, are Fig. 28. Aegina spinosissima, one of the Caprellidae, slightly reduced. [Table-case No. 7.] the numerous species of Gammarus, 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 Eurythenes gryllus and Stegocephalus ampulla, show the large size reached by some species in Arctic Seas, where they swarm in extraordinary profusion ; that Acanthogammarus god- leivskii is one of a host of remarkable species, all closely related Hoplocarida — Stomatopoda. 47 to the common Gammarus, found in Lake Baikal ; and that the Table-case little Chelura terebrans is, of all Amphipoda, perhaps the most No- 7- directly important to man on account of its destructiveness to marine timber referred to above (p. 42). The members of the Sub-order Hypebiidea can generally be recognised by the very large eyes, which may cover almost the whole surface of the head. The first thoracic limbs (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 Capbellidea 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 No' 8‘ segments are separated from the anterior part of the head, bearing respectively the pedunculate eyes and the antennules, and there is a movable 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 Stomatopoda, 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. N°. 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 Fig. 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 Erichthus, Alima, etc. The “ species ” Lysioerichthus edwardsii, of which a specimen is exhibited, has been found to be the larval state of Lysiosquilla glabriuscula. Encarida — 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. — Euphausiacea. „ 2. — Decapoda. Order 1.— Euphausiacea. The members of this Order were formerly included with the Mysidacea in the Order “ Schizopoda.” They are, however, very closely allied to the Decapoda, and are distinguished from the Meg any ctipl banes noruegica, 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. E ■ 50 Guide to Crustacea. Order 2. Decapoda. Table- The gills are arranged typically in three series — podobranchiae, Nos? 9-16. arthrobranchiae, and plenrobranchiae. Only in the aberrant genus Lcucifer 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, Fig. 31. 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 grouped under three Sub-orders : — Sub-order 1. — Macrura. ,, 2.— Anomura. ,, 3. — Brachyura. E nc avid a — Decapo da . 51 Sub-order I. — MACRURA. The Macrura are generally distinguished by the large size of Table- the abdomen, which is symmetrical and not folded under the body. Nos -^g 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 Penaeidea, consists of Table-case prawn-like animals having the first three pairs of legs usually No‘ 9l 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. Penaeus 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 Stenopidea 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 Caridea 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, 52 Guide to Crustacea. Table-case well shown by the specimen of N. undulatipes (Fig. 32) from the N°. 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 Fig. 32. Nematocarcinus undulatipes. [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 A Ipheidae the pincers of the first pair of legs are Decapoda — Mcicru va> usually greatly enlarged and very dissimilar in shape. The second Table-case legs are slender, and have the carpus, or “ wrist,” divided into No' 9- 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. jamcticensis from Fig. 33. The common Prawn, Lcancler serratus, slightly reduced. [Table-case No. 9.] the West Indies. Attention may also be directed to a specimen of the common Prawn ( Lcancler serratus ) (Fig. 33) prepared by a special process so as to retain the translucency of the living animal. In the family Crangoniclae the pincers of the first pair 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 Astacidea (or Nephropsidea) includes the true Table-case Lobsters and Crayfishes. They may be recognised by having the No* 10- 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 54 Guide io Crustacea. Table-case to the preceding, and the male has sexual appendages on the No. 10. 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, is Fig. 34. The “ Norway Lobster,” Nephrops norvegicus, about one-third natural size. [Table-case No. lO.fflBj 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), is found abundantly in certain localities in deeper water than that frequented by the Common Lobster. It is generally sold in London shops Deccipoda — Macrura. 55 under the name of “ Dublin Prawn,” although the chief supplies now come from Scotland and the North-East 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 Ilemi- Fig. 35. Astacopsis franklinii, about ^-th natural size. [Wall-case No. 5.] spheres, the last thoracic sternite is movable. In the Northern Crayfishes, belonging to the family Astaciclae, 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, “ Ecrevisse a pattes rouges,” German, “ Edelkrebs ”), found in France, Germany, Austria, N.W. Russia, S. Sweden, Denmark, &c. Although the name A. fluviatilis is sometimes applied to the English Crayfish, it is more correctly restricted to the Red-clawed species, which does not occur in the British Islands. Table-ease No. 10. 56 Gmde to Crustacea. Table-case No. 10. Table-case No. 11. The “ White-clawecl Crayfish,” Astacus pallipcs (French, “ Ecrevisse 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 Eussia, 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 Eocky 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 Parastacidae, there are no sexual appendages in the male. Numerous species of this family occur in Australia, and Astacopsis spinifera, known as the “ Murray Eiver Lobster,” is used for food. Like the closely allied A. franlclinii (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 Loricata (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 ursus ) of which a Mediterranean specimen is exhibited. It occurs, rarely, off the south-western coasts of England. Dec apod a — Macru ra . 57 Fig. 36. The common Spiny Lobster, Palinurus vulgaris , much reduced. [Wall-case No. 6.] 58 Guide to Crustacea. Tablc-casc The larvae of the Loricata are very unlike those of the related No. 11. 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 Phylldsoma (Fig. 37). Representatives of the extinct family Glyphaeidae are found fossil in rocks of Mesozoic age, from the Trias onwards. In some Fig. 37. 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 from the Jurassic of France is exhibited. In the Tribe Eryonidea 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 , A nornura. 59 The existing species are confined to the deep sea, and, like Table-case 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 Pry on 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, G. subterranea, 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 G. armata from the Fiji Islands is exhibited. Thalassina anomala is a widely distributed tropical species, especially characteristic of mangrove swamps, but sometimes found burrowing in able distance from the sea. Polycheles phosphorus, female. (After Alcock.) [Table-case No. 11.] damp earth at a consider- Sub-Order 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, GO Guide to Crustacea. Tablo^casG front, or rostrum, is not united with the epistome. The sixth pair 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, Birgns, and the family Lithodidae, the members of this tribe have the abdomen soft, not distinctly segmented, and spirally twisted in Fig. 39. The common Hermit-Crab, Eupctgurus bernharclus , in the shell of a whelk, reduced. [Table-case No. 12.] adaptation to the habit of living in the empty shells of Gasteropod Molluscs. 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 typicci, 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, Eupagurus bernhardus (Fig. 39), and one of the largest representatives De capo da— A nomura . 61 of the family, Pagurus pwictulatus, are also placed in this Table-case case. No. 12. The members of the family Coenobitidae are Land-crabs, though their early stages are passed in the sea, and the adults visit the sea periodically. The species of Coenobita carry shells about with them like the marine Paguridae, but the “ Robber-Crab ” or The Coco-nut Crab, Birgus latro, much reduced. [Wall-case No. 6.] “ Coco-nut Crab,” Birgus latro (Pig. 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 often 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 Island, in the Indian Ocean, by Dr. C. W. Andrews, F.R.S., of the No. 12. Geological Department of the Museum, and it shows a specimen of Birg us 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 he 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 Fig. 41. The “ Northern Stone-Crab,” LitJiocles viaia, 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 (uropods) 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 Echidnocerus 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 Galatheidea 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. Fig. 42. Municla rugosa (reduced). [Table-case No. 12.] Several species of Galathea occur on the British coasts, G. strigoscc being the largest. Municla rugosa (Fig. 42) is found in rather deep water in British seas. The family Uroptycliidae includes only deep-sea species and is represented by the brilliantly coloured Eumunida pictct. The family Aegleidae comprises only a single species, Acglea laevis, which is interesting as being the only Anomuran inhabiting fresh water. It is found in South America, 64 Guide to Crustacea. Table-case No. 12. Table- cases Nos. 12-16. especially in mountain streams. In the family Porcellanidae, the 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 ” ( Porcellanct ) 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 Hippidea 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 (Pig. 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- cliyuran 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. Sub-Order 3. — BBACHYURA. The Brachyura, or true Crabs, are distinguished from the other Decapoda by having the abdomen short and bent up under the 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 3 — Oxyrhyncha. ,, 2- Oxystomata. ,, 4 — Cyclometopa. Tribe 5— Catometopa. Fig. 43. Albunea symnista (reduced). [Table-case No. 12.] Decapoda — Br achy lira, Crabs. 65 The Dromiacea or Sponge- Crabs are the most primitive of the Table-case existing Brachyura. The last pair, or the last two pairs, of legs are No’ 12' 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 Fig. 44. Dromia vulgaris. Front view of a specimen carrying on its back a mass of the sponge Clionc celata (reduced). [Table-case No. 12.] somite in both sexes ( sec the exhibited specimen of Dromia laior'). 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 Drorniiclae, in which the last two pairs of legs are generally reduced in size, and are F Guide to Crustacea. 66 Table-case elevated on the back. One of the specimens exhibited, taken in No 12 . x the Bristol Channel, carries as a cloak a specimen of the sponge Clione celata. In the family Dynomenidae, 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 Latreilliidae. 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 ) cuvieri (Big. 45), Fig. 45. 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 Homolodromiidae. 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 Decap oda — Brachyu ra. 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> 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 Leucosiidae 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 Guide to Crustacea. Table-case No. 13. Table-case No. 14. 68 ; of the genus Ebcdici. They are small Crabs, resembling the pebbles among which they are found. Specimens of Ebcdici tubcrosa 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 Baninidae 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 Mcitiitci. The “frog-crab,” Banina scabra, is, in general appearance, one of the most striking and aberrant of the Brachyura. In the Tribe Oxyrhyncha 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 Maiidae 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, a common British species which has the long and slender legs that are typical in the group. Hucnia 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 De capo da — Brachyura. 69 coasts of England, Mctia squinaclo, a large specimen of which is Table-case exhibited in Wall-case No. 4. N0, 14‘ Fig. 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) kaempferi (Eig. 46), the largest of existing Arthropoda, of which two male specimens 70 Guide to Crustacea . Table-case and a female are mounted above the Wall-cases at the south end isr°. 14. 0f the Gallery. They were coloured after a drawing of a live specimen by a Japanese artist. In the family Parthenopidae, 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 horridcc exhibited, the carapace and limbs are remarkably rugged and uneven. Table-ca ;o The Crabs belonging to the Tribe Cyclometopa have the N°. 15. 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 Eiver-crabs, all the members of this tribe inhabit the sea. In the large and very varied family .Xanthiclae, the carapace, as a rule, 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 w'hich, X. 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, Pseudocar cinus gigas, a specimen of which is mounted above Wall-cases Nos. 5 and 6. A specimen of Zozyinus 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. 13. 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 Crahs) may be recognised by the flattened, paddle-shaped, last De cap oda —Brachyii ra . 71 pair of legs. Two British species of the genus Portunus are exhibited : the colours of P. depurator have been carefully copied from a living individual, and the specimen is mounted on a sample of the shell-gravel on which it was actually caught. The large Pseudocar cinus 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 East. The Common Shore -Crab, Car cinus mamas, is also referred to this family, although the paddle shape of the last legs is not so marked as in the more typical Portuhidae, Table- case No. 15. Guide to Crttstacea. Table-case No. 15. Podophthalmus vigil (Fig. 48) is 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 Cancridac are distinguished from the preceding families by having the antennules folded longitudinally instead of transversely. Fig. 48. Podophthalmus vigil (reduced). [Table-case No. 15.] 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 includes Crabs which are allied to the Cancridae, but have long antennae, and the third maxillipeds are Decapo da — Br achy lira . elongated, extending over the front edge of the moutli-frame. The Table-case latter character recalls the Oxystomata, which the members of this No- 15- 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 Female. Male. Fig. 49. Corystes cassivelaunus (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 Catometopa the carapace is typically more or less Table-case quadrate, with the front strongly bent downwards : the mouth- No- 16, 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 Geocar ciniclae (or Gecarciniclae ) comprises the true Land-Crabs, although some members of the other families also 74 Guide to Crustacea. Table-case are almost entirely terrestrial in habits. The carapace is more or No. 16. jegs transversely oval, and the front is of moderate breadth. The branchial regions of the carapace are generally swollen, and the lining membrane of the gill-chamber is richly supplied with blood- vessels, and acts as a lung. Typical genera are Geocarcinus, Car- clisoma, 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 litter ata is widely distributed throughout the Indo- Pacific region, and seems to be equally at home in freshwater 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, ii. 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 greater size in the male sex. The large, brightly coloured claws Decapo da — Brackyura . 75 are used by the males in fighting with each other, and are also Table-case believed to serve to attract the females. No' 16' Gclasimus 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. Fig. 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 Ascidians 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 Pinnctxodes chilensis lying in a 76 Guide to Crustacea . Table-case large pouch which is formed by enlargement of the terminal part No. 16. 0f tiie 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 Fig. 51. Macrophthalmus pectinipes, reduced. [Table-case No. 16.] a more or less triangular front, and in other respects show some resemblance to the Oxyrhyncha. Halicarcinas planatus, of which specimens obtained by the “ Discovery ” Expedition at the Auck- land Islands are exhibited, is found throughout the whole of the “ Sub- Antarctic ” region, occurring at such distant points as the Falkland Islands, the Cape, Kerguelen Island, and New Zealand. Trilobita. t / Class 2.— TRILOBITA. The members of this class are known only in the fossil state, Table-case and are characteristic of the strata of the Palaeozoic era. They No- 17- 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 Fig. 52. Reconstruction of a Trilobite, Triarthrus becld. 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 78 Guide to T rilobita. Table-case mesosoma), which vary in number from two to as many as twenty- N°. 17. nine, were inovably jointed together in the living animal. Each consists of a vaulted dorsal area (the tergurn), 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 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-crabs 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-c 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 Palaeozoic period, at the close of which the group became extinct. A restoration and drawings of Triarthrus becki 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. Table- cases Nos. 19-26. Class 3.— ARACHNIDA. The Arachnida, a class which includes such familiar animals as the spiders, scorpions, and mites, constitutes one of the main 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-like 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 Euarachnida 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 group of doubtful affinities. Table of Classification of the Arachnida. Class— AEACHNIDA. Sub-class 1— EUARACHNIDA. Division A. — Delobranchia. Order 1. — Xiphosura (King-crabs). ,, 2. — Gigantostraca (Eurypterines — Eossil forms). Euarachnida — X ip ho sura. 81 Division B. — Embolobranchia. Order 1. — Scorpiones (Scorpions). ,, 2. — Pedipalpi (Whip-scorpions and their allies). ,, 3. — Palpigracli. ,, 4. — Aranecce (Spiders). „ 5. — Solifugae (False Spiders). ,, 6. — Pseudoscorpiones (False Scorpions). „ 7. — Podogonct. „ 8. — Opiliones (Harvest-men). ,, 9. — Acari (Mites). Sub-class 2.— PYONOGONIDA. Sub-class i.— 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 . — DEL OB BA NCHIA. 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 Wa'l/case P°typhemus) differs from the Oriental species in having the No. 7. 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 Garcinoscorpius ) 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 ( Xiphosura joolyphemus) . About 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. Gigantostraca. 83 Order 2.— Gigantostraca (Eurypterines). In the Gigantostraca the sixth (or fifth and sixth) pairs of the 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). Restoration of Eurypterus fischeri (after Holm). a — Appen- dages of prosoma, b — Sternal plate of prosoma, c — Appendage believed to distinguish the female sex, perhaps an ovipositor. d.— 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. Table-case No. 19. 84 Guide to Arachnida. Table-case No. 19. Table- cases Nos, 19, 20. 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 (. Eurypterus fischeri) 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.—EMBOLOBBANCHIA. 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 Scorpiones . 85 are filled up with lamellae, which are arranged like the leaves of a Table- hook 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 ( Eoscorpius and Gyclo- 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 Palavi- naeus) are of very large size, one or two of them reaching a length of about nine inches. There are several European species, the largest of them belonging to the genus Buthus , which has two representatives in Buthus occitanus (slightly reduced). 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 Europe. They live under stones and in other obscure situations, and sometimes make their way into houses in the wet weather ; there are four European species. An allied genus {B disarms'), with a single species, which has lost all trace of eyes, is restricted in distribution to the Eastern Pyrenees. One of the Buthidae -( Isomctrus maculatus ) 86 Guide to Arachnida. Table- cases Nos. 19, 20. 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 hark 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 ( Centrums 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. Pandinidae. 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 , Opistlioph- thalmus , Urodacus, etc.) Fam. 2. — Bothriuridae. This family is confined to South America and Australia. It is characterised by having 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 Pedipalpi. 87 tropical Africa, Madagascar, and Australia. The sternum is Table- pentagonal, as in the Pandinidae, but is variable in form, being ^gSe|0Nos' 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, lurus, Euscorjjius , Broteas, etc.). Pam. 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 : Buthns, Cen- trum's, 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. No" 21 ' 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. — UBOPYGI. 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. Tribe— UBOTBICHA. 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 Fig. 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 Geralimirci, 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 Pedipalpi . 89 crush with their powerful pincers. When irritated they eject an Table-case offensive acid secretion, which is the product of two large glands No- 21* opening on the end of the last abdominal segment. The female, after laying her eggs, carries them about attached to the underside of her body. Tribe- 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. Sub-order II. AMBLYPYGI. The cephalo- thorax of these Pedipalpi is wider than long. All the segments of the legs of the first pair, with the exception of the basal three, are sub-divided so as to form a long flagellum. Fig. 58. Damon johnstoni (one-half natural size). V 90 Guide to Arachnida. Table-case No. 21. 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. Bespiratory organs are absent. These interesting Arachnids were first dis- covered by Professor Grassi, who described and figured an Italian species in the year 1885. They are minute creatures, usually measuring less than two millimetres, or barely one-twelfth of an inch in length. All the known species belong to the genus Koenenia, 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 viewT in Table- case 21. Fig. 59. Koenenia mirabilis (magnified). A raneae > 91 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 ^^g^08' 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 few7 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 Sicariidae (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. 92 Guide to Arachnida. Table- Mention must also be made here of the curious sound-producing ^se|gNos' organs which are found in many of the Theridiidae. 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, etc.) 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 A raneae. 93 floccnlent web, as on an autumnal day in England. The ship was Table- sixty miles distant from the land, in the direction of a steady ^se2sgNos' 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 he produced by the entanglement of the single threads. . . Spiders are divided into two sub-orders : 1. Mesothelae. 2. Opisthothelae. Sub-Order 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- Pig. 60. tolycosa, etc.). There is but Liphistius desuitor. a single family with two genera (Liphistius and Anadiastothele), which occur in Burma, Malacca, 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 desuitor is exhibited in Table-case 22. 94 Guide to Arachnida. Sub-order 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.— Mygalomorphae. 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. Eam. — Aviculariidae. 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 cambridgi ) 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 A raneae . 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‘ 22‘ 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 ( Ephebopus murinus ), Wall-case together with examples of the spider itself, are shown in Wall- •No* 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. — Gtenizidae. 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 ( Pseudidiops , etc.) 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 wallacei), 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. Guide to Arachnida. Table-case No. 22. Wall-case No. 7. Table-case No. 23. 96 Fam. — A typidae. The two genera ( Atypus and Calommata ) which compose this family differ from the Avicnlariidae 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 or lies loosely on the surface of the ground; 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 abboti ), which are spun against the trunk of a tree, are exhibited in Wall-case 7. Tribe ii. — 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 ( Epciridac ) . The spiders of this family are sedentary in habit, catching their prey by means of webs. Some of them spin orb-webs, others 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 (A ranea ( Epeira ) 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 98 Guide to Arachnida. Table-case turns upon him with murderous intent during No‘ 23' courtship, as female spiders commonly do. Some of the tropical Argiopidae ( Gasteracantha, , etc.) have 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 with processes resembling the thorns with which the tree is beset. The Argiopidae are cosmopolitan in distribution. Fig. 63. Tarsal-comb of the fourth leg of Theridion tejpida- riorum. Magnified. (After F. 0. Pick- ard-Cambridge.) 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 wdde 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. A Theridiid Spider (Lathrodectus tredecim - gutta tus), x 2. A raneae. 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 wTandering 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 lie 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, etc. The Crab-spiders belonging to the sub-family Philodro- minae are more active in habit, and trust to their speed for the capture of their prey. A sketch in colour of a common British flower- spider ( Misumena 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 Flower-spider, Misumena vatia, x 2. (After Blackwall.) 100 Guide to Arachnida. Table-case No. 23. Specimens of this spider have been found at University College, London, and also at Bristol, but since tropical conditions appear to he 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 Hippaseae, 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, a 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 tarmtula (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 A raneae . 101 webs in the corners of cellars and ont-houses. The spiders of the Table-case genus Desis, which occur on the coasts of South Africa, Malay No- 23- 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 European 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. Eam. — Eresidae. 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 ( Eresus cinnaber inus) has been found on two or three occasions in the South of England. Eam. — Eysderidae. 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. Eam. — 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 No. 23. Table-case No. 24. Of the British jumping spiders, E^iblemum scenicum, a species 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 Myrmaraclnne 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). _ „ The Solifugae have Jumping Spider, Epiolemum scenicum, x 8. ~ n (After Blackwall.) some superficial re- semblance to the spiders, but may be easily distinguished from them by their having 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. 103 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) is 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 to occur in forests. After nightfall in the 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 Fig. 67. Galeodes arabs (three-fourths natural size). 104 Guide to Arachnida. Table-case the world. In Europe they are found in Spain, Greece and No' 24' Southern Eussia, whilst in America, they are distributed from the Southern States of the Union to the Andean Chain in Chile and the Argentine Eepublic. They are entirely absent from Austra- lasia, China and Japan. There are three families: — 1. Galeodidae ; 2. Solpugidae ; 3. Hexisopodidae. Eam. — 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 ( Bhagodes , etc.) are slow and clumsy in movement. Eam. — Hexisopodidae. 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 P sen do sco rpion es. 105 by a single plate, which, however, sometimes shows traces of Table-case segmentation. There are no median eyes, but one or more lateral No- 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 cephalothorax and the abdomen (opisthosoma), but the large dorsal plate of the praegenital segment (which is generally suppressed in the Euarachnida) lies between these two regions. Eleven abdominal somites can often be distinguished, and none 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, etc., and several species have been found on merchant-ships ; not uncommonly specimens may be met with clinging to the legs of flies or beneath the wing-cases of beetles. One of the British species ( Obisium mari- timum ) 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) Panctenodactyli, (2) Hemictenodactyli. Drawings illustrating the main points of difference between these sub-orders are placed in Table-case 24. Fig. 68. Chelifer cancroides, x 5. (After Berlese.) 106 Guide to Arachnida. Table-case No. 24. Sub-order I.— PANCTBNODAOTYLI. The members of this sub- order have the first appendage of 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. Sub-order II.— HEMICTENODACTYLI. 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) Obisiidae. 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 surface of this membrane. The abdomen (opisthosoma) consists of only four visible segments, in addition to a tubular ring encircling the anus. A striking the position of the copuiatory at the end of each walking-leg Diagram of a species of Cryptostemma, to show the characters of the Podogona. ( X 4.) peculiarity of these animals is organs, one of which is placed 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 ( Gryptostemma harschi) (and also enlarged drawings of the species) are also exhibited in Table-case 24. Podogona, Opiliones 107 The existing species of Podogona are referable to the family Table-case Gryptostemmatidae. They are small Arachnids, barely reaching •No- 24- 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- No- 25 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, 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). Sub-order I. — LANIATOEES. In these Opiliones the palp is often stout and furnished with a strong prehensile claw. There is a single claw on each of the Fig. 70. Gonyleptes chilensis. 108 Guide to Arachnida. Nobl25CaSe ba*rs’ but the legs of the posterior pairs have 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. Sub-order II. — 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, etc. 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. Sub-oeder III.— ANEPIGNATHI. Stylocellus sumatranus. ~ x 2 One ot the most important distin- guishing 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 Sironidae, the members of which chiefly occur in the East 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. No> 25, Drawings of Stylocellus sumatranus, 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 ^gS25 9g 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. 5. Astigmata. 2. Cryptostigmata. 6. Vermiformia. 3. Metastigmata. 7. Tetrapoda. 4. Prostigmata. Sub-order 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 segmentatus is exhibited in Table- case 25. 110 Guide to Arachnida. Table-case No. 25. Table-case No. 26. Sub-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. Sub-order III.— 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, like beetles, but apparently for the purpose of loco- motion, not of parasitism. Some members, however, are parasitic upon mammals and birds. Fam. — Ixodidae. Gamasus coleoptratorum (mag- „ nified). (After Berlese.) The coalesced basal segments ol 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 A cari. Ill to lay their eggs upon the ground, under stones, in grass, the crevices Table-case of walls, etc. The Ixcydidae are divided into two sub-families. N0, 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- sians) is also known to transmit spirillosis amongst its hosts. Sub-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 Fig. 73. family are known to convey infectious Margaropus annulatus, the Cattle n. J , . , , Tick; distended female, x 5. 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). Sub-obdee 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 : Trombidiidae, Hydrachnidae, Halacaridae , and Bdellidae. 112 Guide to A rachnida. Table-case No. 26. Fam. — Trombidiiclae. 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 various 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 {Tetr any elms 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, etc. They are widely distributed and there are numerous British species. F am . — Halacaridae . In the Halacaridae the buccal organs are carried on a distinct rostrum ; the appendages of the first pair are either styliform 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. A cari. Fam. — Bdcllidae. 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) is common on our sea-coasts. SUB-OEDEE Y. ASTIGMATA. In these Acari, which are closely allied to the Prostigviata, there is no trace of a respiratory system. Many of them are parasitic, others are free-living and feed on animal and vegetable refuse. It is to this sub -order that the mite ( Sarcoptes scabiei) which is the cause of itch belongs. The cheese mite ( Tyroglyphus 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 tuft 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. i | House-mite, Glycyphagus domesticus , X 50 (after Michael). Table-case No. 26. Fig. 74. Sarcoptes scabiei , the itch mite, x 100 (after Canestrini). 114 Guide to Arachnida. Table-case No. 26. Sub -order VI. — VERMIEORMIA. The Acari belonging to this sub-order are degenerate, parasitic 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. Fig. 76. Demodex caninus , ven- tral view of female. Greatly magnified (after Canestrini). Fig. 77. Ventral view of a gall- mite, Drio'phyes sil- vicola, x 135 (after 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, Eriophyidae ( 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. 115 other excrescences of the stem or leaves, but a number of Table-case species are wandering forms, or live in the galls of other species. No- 26, A drawing of one of these mites ( Eriophyes silvicola), which produces galls on the leaves of the stone-bramble (JRubus saxatilis), 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 ( Eriophyes ribis) and of the plum mite ( Eriophyes pruni), 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, Diagram of a Pycnogonid, Nymphon ( Boreonymphon ) robustum. 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 (Pig. 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. Pour pairs of very long legs (iv.-vii.) 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 (i.) are chelate (or pincer-like), and overhang a tubular proboscis on which is the opening of the mouth ; the second pair (ii.) are sensory palps, placed at the sides of the proboscis ; the third pair (hi.), placed Guide to Arachnida . Table-case No. 26. 116 just behind the last, are used, in the male sex, for carrying the eggs, and are known as “ ovigers.” 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 Pycnogonida 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 of some or all the pairs. A remarkable fact in the breed- ing habits of these animals is 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 Pycnogonida 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 Pycnogonum littorale , which is common between tide- marks on the British coasts ; Nymphon (. Boreonymphon ) 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. Fig. 79. Decolopoda australis, a ten-legged Pycnogonid from the Antarctic Seas. Slightly reduced. [Table-case No. 26.] Pentastomida. 117 APPENDIX TO ARACHNIDA. PENTASTOMIDA. The Pentastomida, or Linguatulida, represented in Wall- case 7 by Pentastomum armillatum from an African python, 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 Fig. 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 No. 7. 118 Guide to Onychophora. Wall-case (see plan on p. 10). Class 4.— ONYCHOPHORA. This 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 Eoperipatus from Malacca ; while figures illustrative of the natural habit are given of Peripatopsis capensis , of Eoperipatus viridimaculatus from New Zealand, and Paraperipatus from New Britain. It will be seen, therefore, that the distribution of this form is extremely wide, Fig. 81. 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 ringed 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 Peripatus. 119 the most gifted naturalists of his time, had the opportunity of Wall-case dissecting freshly killed specimens at the Cape of Good Hope. on pP10) When opened under water a glistening appearance revealed 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 tracheae) 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 eggs 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 egg is minute, and almost entirely devoid of yolk. In the Gape species (. Peripatopsis capensis) the eggs are larger and there is some yolk. In the eastern species (e.g., Eoperipatus horsti) 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. The species 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. 120 Guide to Myriopoda. Table-case No. 27. 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 Ohilopoda, 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 “ gnctthochilarium,” 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, Diplopoda. and large tnfts of similar hairs project from the sides of each Table-case segment ; the last segment is furnished with a tuft of long hairs. ^°’ The mouth-parts consist of paired mandibles, Fig. 82. Polyxenus lagurus, the English bristly milli- pede, x 12. 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, Polyxenidae, with two genera; one species (Polyxenus lagurus) occurs 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 usually fuse'to form a complicated gnatho- chilarium. There are three orders of Chilognatha. 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, but are very rare in America. The typical dark variety of Glomeris marginata, the Pill-Millipede, occurs in Great Britain and Ireland. In Southern Europe a large number of sub-species and varieties of Glomeris Fig. 83. Sphaerotherium punctatum (slightly enlarged). 122 Guide to Myriopoda. Table-case have been distinguished by differences in colour. The tropical No. 27. forms (Sphaer other ium, 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, Glomeridesmidae , 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 auxiliary 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 I.— LYSIOPETALOIDEA. The body of these millipedes is slender and sub-cylindrical, and the number of segments is large and variable. They have a wide distribution. Sub-order II.— 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 , etc.), and Siphonophoridae ( SiphonopJiora , Polyzonium, etc.). Sub-order III.— CHOEDEUMOIDEA. 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 European and North American forms. The sub-order is represented in this country by two species, the better known being Atractosoma polydes?noides. D ip lop o da , Pauropoda. Sub-order IV. — IULOIDEA. 123 The body is elongated and cylindrical in these millipedes, and Table-case the number of segments differs greatly in the various forms. Stink- No- 27 • Fig. 84. lulus varius. Natural size. (After Koch.) glands are present. In the male the seventh segment is limbless. In the tropical regions some of the Iuloidea (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. Sub-order Y. — 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 in distribution ; there are several British species, which mostly belong to the genera Polydesmus and Brachydesmus. Fig. 85. Polydesmoid millipede, Eurydesmus angulatus. Slightly enlarged. (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 an inch. The body-segments Guide to Myriopoda. 124 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, “ Pauropus 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, aud to their retiring habits, they are still very incompletely known. They have Fig. 86. Fig. 87. Pauropus huxleyi, x 24. Scutigerella immaculata, x 8. (After Lubbock.) (After Latzel.) been found in Europe, tropical Asia, aud North and South America, and it is possible that they have a very wide distribution. There are three families. Drawings of Pauropus and Eurypauropus, 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. Symphyla, Chilopoda . 125 These minute Myriopods have a wide distribution ; they have Table-case been found in Europe, India, Java, Sumatra, South Africa and •No‘ America. A few species occur in this country. There is a single family, S colop endrellidae, 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 11 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 swift- 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. Each 126 Guide to Myriopoda. Table-case somite, with the exception of the first and last, is furnished N°. 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 head-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 Geophilus longicornis PurPoses> and als0> is believed, as a means (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 a rule 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 Fig. 88. 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 No- 28, (. Scolopendra gig as), which is an inhabitant of the West Indies and South America, sometimes reaches £ genus Alices, which is confined to for the very peculiar structure of modified to form a stridulatory organ, whereby the animal emits a hissing sound. Ethmostigmus trigonopodus is the largest and commonest of the tropical African species of centipedes, and it is 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. subspi- 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- ber as in the Lithobiomorpha. There is only a single species which occurs in Tasmania. . length of almost a foot. The tropical Africa, is remarkable the posterior legs, which are 'rater ostigmns tasmanianus), 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 Lithobius 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 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- morpha, are also very long, and have the terminal segments many- jointed. 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, etc.) 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. Fig. 90. Scutigera ( Cermatia ) forceps (after Kingsley). INDEX. 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 Adbunea, 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 Anepignatbi, 108 Anomura, 59 Anostraca, 26 Antenna of Crustacea, 15 Antennule of Crustacea, .15 Antbracomarti, 107 Ant-like Spiders, 100, 102 Appendages of Crustacea, 15 ; of Aracbnida, 80 ; of Trilobita, 78 ; of Onycho- pbora, 119 Apseudes, 40 (fig.) Apus, 26 (fig.) Aracbnida, 9, 80 Aracbnomorpbae, 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 Artbrobranchia, 17 Artbropoda, 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 B. Balanus, 32 (fig.), 34 Barnacles, sessile, 33 ; stalked, 32 Basis, 15 Bathynomus, 41 (fig.), 42 Bdella, 113 Bdellidae, 113 Beetle-mites, 110 Belinurus, 82 Belisarius, 85 Bird-eating Spiders, 94 Birgus, 60, 61 (fig.) Black-currant Mite, 115 Bopyrus, 44 Boreonymphon, 115 (fig.), 116 Bothriuridae, 86 Bothriurus, 86 Brachydesmus, 123 [ Brachyura, 64 Brain of Crustacea, 19 | Branchiae of Crustacea, 17 j Branchial cavity, 15 ; la- mellae, 81 Brancbiopoda, 25 Branchiostegite, 15 Brancbiura, 30 Bristly Millipede, 121 (fig.) Broteas, 87 Browne, 27 Butheolus, 85 Butbidae, 87 Buthus, 85 (fig.), 86, 87 Caerostris, 98; Galappa, 67, 70 Calappidae, 67 Gallianassa, 59 Calling Crab, 74 Calocalanus, 30 (fig.) Galommata, 96 Calymene, 78 (fig.) Camarostome, 109 Gambarus, 56 Cancer, 72 Cancridae, 72 Capitulum, 32 Caprellidae, 24, 47 Caprellidea, 47 Carapace of Crustacea, 13 ; of Aracbnida, 80 Carcinoscorpius, 82 Garcinus, 35, 44, 71 Gar disoma, 74 Caridea, 51 Car pi Lius, 70 Catometopa, 73 Catophragmus, 33 Caudal fork, 29 Centipedes, 125 Centrums, 86, 87 Cephalic shield, 77 Cepbalotborax of Crus- tacea, 14; of Arachnida, 80 Ceratiocaridae, 37 Cercophonius, 86 K i3° Index . Cermatia, 128 (fig.) Cervical groove, 15 Charontinae, 90 Cheese-mite, 113 Chelate, 17 Chelicerae, 81 Chelifer, 105 (fig.), 106 Cheliferidae, 106 Cheliped, 17 Chelura, 42, 47 Clielypus, 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-nnt Crab, 60, 61 (fig.) Cocoon of Araneids, 92 Coenobita, 61 Coenobitidae, 61 Colobognatba, 122 Colossendeis, 116 Colulus, 96 Commensalism, 60 Concbostraca, 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 Craterostigmomorpba, 127 Graterostigmus, 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 Cyamidae, 47 Cyclometopa, 70 Cyclophthalmus, 85 Cymothoidae, 42 Cypris, 29 (fig.) Cypris-stage of .Cirripedes, 33 Cythereis, 29 (fig.) D. Damon , 89 (fig.) Daphnia, 27, 28 (fig.) Darwin, 34, 92 Decapoda, 50 Decolopoda, 116 (fig.) Delobranchia, 81 Demodex, 114 (fig.) Demodicidae, il4 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. Ebalia, 24, 68 Ecdysis, 21 Echidnocerus, 62 Edible Crab, 22, 72 Eggs of Lobster, 20 Embolobrancbia, 84 Endopodite, 15 Eoperipatus, 118 Eoscorpius, 85 Epeiridae, 97 Epeira, 97 Ephebopus , 95 Epiblemum, 102 (fig.) Epicaridea, 44 Epipodite, 16 Eresidae, 101 Eresus, 101 Erichthus, 48 Eriophyes, 114 (fig.), 115 Eriopbyidae, 114 Eryon, 59 Eryonidea, 58 Estheria, 27 (fig.) Ethmostigmus , 127 Euaracbnida, 81 Eucarida, 49 Euchaeta, 30 Eucopepoda, 30 Eumunida, 63 Eupagurus, 60 (fig.) Eupbausiacea, 49 Eurydesmus, 123 (fig.) Eurypauropus , 124 Eurypterines, 83 Eurypterus, 83 (fig.), 84 Euscorpius, 85, 87 Eurythenes, 46 Exopodite, 15 Exoskeleton, 12 Eye-stalks, 17 F. 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, 103 (fig.), 104 Galeodidae, 104 Gall-mites, 114 Gamasidae, 310 Gamasus, 110 (fig.) Gammaridea, 45 Gammarus, 45 (fig.), 46 Garypidae, 106 G aster acantha, 97 (fig.), 98 Gastric mill, 17 Gelasimus, 74, 75 (fig.) Geocarcinidae, 73 Geocarcinus, 74 Geopbilomorpba, 125 Geophilus, 126 (fig.) Index. 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 (fig.), 32 (fig.) Graeophonus, 90 Grapsidae, 74 Grapsus, 74 Grassi, 90 Green glands, 19 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 Heteropodcv, 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 I Ibla, 33 Idotea, 43 Insecta, 9 Internal Anatomy, of Lob- ster, 17, 18 (fig.) Iphinoe, 39 lsometrus, 85, 87 Isopoda, 41 ; parasitic, 42, 44 Itch-mite, 113 (fig.) Iuloidea, 123 lulus, 123 (fig.) Iurus, 87 Ixodidae, 110 Ixodinae, 111 J Joint, 13 Jumping Spiders, 101 K Kaempferia, 69 (fig.) King-crabs, 11, 81, 82, (fig.) Koenenia . 90 (fig.) L Lamina, 105 Land-crabs, 61, 73 Laniatores, 107 Larvae of Lobster, 21 ; of Stomatopoda, 48 ; of Loricata, 58 Laterigrade-spiders, 99 Latreillia, 66 Latreilliidae, 66 Lathrodectus, 98 (fig.) Leander, 44, 53 (fig.) Legs of Crustacea, 15, 17 Lepas, 31 (fig.), 32 (fig.) Leptodora, 28 Leptomysis, 39 Leucifer, 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 Kiver, 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 Lysioerichthus, 48 Lysiopetaloidea, 122 Lysiosguilla, 48 M. Macrocheira, 69 (fig.) Macromysis, 39 Macrophthalmus, 72, 75, 76 (fig.) Macropodia, 24, 68 Macrura, 51 Maia, 24, 69 Maiidae, 68 Malacostraca, 36 Malleoli, 103 Mandible of Crustacea, 15, 16 Mange, in dogs, 114 Margaropus, 111 (fig.) Marine mites, 112; spider, 101 Mastigoproctus, 88 Matuta, 67 Maxilla of Crustacea, 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 Index. 132 Myrmarachne, 102 Mysidacea, 38 Mysis, 38 (fig.) Nauplius, 33 Nebalia, 36 (fig.) Nematocarcinidae, 51 Nematocarcinus, 52 (fig.) Nematos celis, 49 Nephila, 97 Nephrops, 54 (fig.) Nephropsidea, 53 Neptunus, 71 Nervous system of Crus- tacea, 19 Northern Stone-Crab, 62 Notaspis, 110 Notostigmata, 109 Notostraca, 26 Nymphon, 116 0. Obisiidae, 106 Obisium, 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 Opisthophthalmns, 86 Opisthosoma, 80 Opisthothelae, 94 Orb-webs, 97 Orcliestia, 45 Oribatidae, 110 Ornithodoros, 111 Ostracoda, 28 Oviger, 116 Oxyrbyncba, 24, 68 Oxystomata, 66 P. Paguridae, 60 Paguridea, 60 Paguropsis, 60 Pagurus, 61 Palaemon, 53 Palaemonidae, 53 Palamnaeus, 85 Palinuridae, 56 Pcilinurus, 56, 57 (fig.) Palp of Aracbnida, 81 ; of Crustacea, 17 Palpatores, 108 Palpigradi, 90 Palpognatbs, 125 Panctenodactyli, 105, 106 Pandalidae, 52 Pandalus, 52 Pandinidae, 86 Pandinus, 85, 86 Pantopoda, 115 Pcmulirus, 56 Paraperipatus, 118 Parasites, modifications caused by, 23 Par ilia, 67 Paromola, 66 Parthenope, 70 Parthenopidae, 10j Pauropoda, 9, 123 Pauropus , 124 (fig.) Pedipalpi, 87 Pedunculata, 32 Penaeidea, 51 Penaeus, 50 (fig.), 51 Pennella, 30 Pentanymphon, 116 Pentastomum, 117 (fig.) Peracarida, 38 Pericardium of Crustacea, 18 Peripatopsis, 118 Peripatus, 118 (fig.) Pbalangiidae, 108 Phalangium, 108 Philodrominae, 99 Philomedes, 29 (fig.) Phosphorescence, 49, 51, 59, 126 Pbreatoicidea, 42 Phronima, 47 Phyllocarida, 36 Phyllopoda, 25 Phyllosoma, 58 (fig.) Pbytoptidae, 114 Pill-Millipede, 121 Pinnaxodes, 75 Pinnotheridae, 75 Planes, 74 Plankton, 29 Platydesmidae, 122 Platydesmus, 122 Platyonychus, 72 Platyrrhachus, 123 Pleopod, 15 Pleurobrancbia, 17 Pleuron, 14 Plum mite, 115 Podobranchia, 17 Podocopa, 29 Podogona, 106 Podophthalmus, 72 (fig.), 75 Podosomata, 115 Poison-glands, 86, 91 Poison-jaws, 125 Poison of spiders, 98, 100 Poliochera, 107 Pollicipes, 32 Polycheles, 59 (fig.) Polydesmoidea, 123 Polydesmus, 123 Polyxenidae, 121 Polyxenus, 121 (fig.) Polyzonium, 122 Porcelain Crab, 64 Porcellana , 64 Porcellanidae, 64 Porcellio, 44 (fig.) Portunidae, 70 Portunion, 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, 71 (fig-) Pseudoscorpiones, 104 Psoroptes, 113 Pterygotus, 84 Pulmonary sacs, 91, 93, 94, 96, 128 Pycnogonida, 115 Pycnogonum, 116 Pygidium, 78 R. Banina, 68 Raninidae, 68 Respiratory system of Arachnids, 80 Bhagodes, 104 Rhizocepbala, 35 Index. 33 River-Crabs, 72 Robber-Crab, 61 (fig.) Rostrum of Acari, 109 ; of Crustacea, 13 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 Sicariidae, 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 Sphaer other ium, 121 (fig.) Spiders, 91 Spider-Crabs, 68 Spinnerets, 91, 93, 94, 96 Spinning-mites, 112 Spirillosis, 111 Spirobolidae, 123 Spirostreptidae, 123 Sguilla, 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, 91, 127 ; ridges, 103 Stylocellus, 108 (tig.) Stylonurus , 84 Swimmerets, 13 Swimming Crabs, 70 Symphyla, 9, 124 Syncarida, 37 T Tachypleus, 82 Tail, 87 Tail-fan, 51 Talitrus, 45 Tanaidacea, 40 Tarantula, 100 Tarantulidae, 90 Tarsal comb, 98 (fig.) Tartarides, 89 Ta smanian 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 Tetranyclms, 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 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 Trombidium, 112 Tubicinella, 34 Turrilepas, 33 Tyroglyphus, 113 U Uca, 74 Urodacus, 86 Uropod, 15 Uroptychidae, 63 Uropygi, 87 Urotricha, 87 V 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 X Xanthidae, 70 Xantho, 70 Xenesthis, 94 Xiphosura, 11, 81 Xiyhosura, 82 (fig.) Z Zozymus, 70 Zephronia, 122 Zephroniodesmus, 122 GUIDE-BOOKS. ( The Guide-books can be obtained only at the Museum. Postage extra.) General Guide to the Museum, 8vo. 3d. 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