Part 4 (1/2)

The third section of the Reptantia, the _Anomura_, comprises for either bent upon itself or, if extended, s are co Thethe section differ widely in their general appearance

The _Galatheidea_ (Plate VI) are small, flattened, lobster-like animals which have the abdomen bent under the body In one family (_Porcellanidae_) the ani 41, p 113), but they uished from the true Crabs (Brachyura) by the fact that there are only three pairs of walking legs behind the great chelae, the last pair of legs being very small and carried folded up at the sides of the body, or even within the gill chaosa_ BRITISH (REDUCED)]

The _Thalassinidea_ are small lobster-like anienerally a38, p

103)

[Illustration: _PLATE VII_

THE COMMON HERMIT-CRAB, _Eupagurus bernhardus_, IN THE Shell OF A WHELK (REDUCED)

(_Frouridea_ includes the Heruridae_) and their allies The typical Hermit Crabs (Plate VII), which are familiar objects in seaside rock-pools, live in the empty shells of Whelks and other Gasteropod Molluscs, which they carry about with them as portable shelters The structure of the animals is modified in adaptation to this curious habit The abdo life by the borrowed shell, is soft and unarmoured, and is spirally twisted The swis in the female, are much reduced, and are usually present only on one side of the body The uropods no longer for the hind part of the body into the coils of the shell

One of the chelipeds iswhen the animal withdraws into its shelter In tropical countries certain Hermit Crabs (_Coenobitidae_) have become adapted to a life on land, and one of these, the well-known Coconut Crab, or Robber Crab (_Birgus latro_), which is the largest species of the tribe, has given up the habit of protecting itself with a shell, and its abdo armour on the upper side The marine _Lithodidae_--to which the British Stone Crab, _Lithodes ht to have little resemblance to the Hermit Crabs, for they have the abdomen very small, and tucked up under the body as in the true Crabs Like the Porcellanidae, mentioned above, however, the Lithodidae have only three pairs of walking legs behind the chelipeds, the last pair being feeble and usually folded out of sight within the gill chambers The relationshi+p of the Lithodidae to the Hermit Crabs is shown by the abdomen, which is more or less twisted to one side, and has swi in the male

[Illustration: _PLATE VIII_

THE ”NORTHERN STONE-CRAB,” _Lithodes maia_, MUCH REDUCED THE LAST PAIR OF LEGS ARE FOLDED OUT OF SIGHT IN THE GILL CHAMBERS

(_From Brit Mus Guide_)]

The _Hippidea_ are curious little Crabs found burrowing in sandy beaches in the warmer seas They have the abdos flattened for shovelling the sand

The BRACHYURA, or true Crabs, foruished by having the abdomen reduced to a tail-flap, which is doubled up under the cephalothorax, and is usually without any trace of the uropods which are present in all the groups already le exception of the Lithodidae At the sides of the head the side-plates of the carapace become firmly soldered to the ”epistome,” a plate which lies in front of the mouth, and in this way there is formed the ”mouth-frame,” within which lie the jaws, covered in by a pair of ”folding-doors” formed by the flattened third maxillipeds

[Illustration: _PLATE IX_

THE COMMON Shore-CRAB (_Carcinus aris_, CARRYING ON ITS BACK A Mass OF THE SPONGE _Clione celata_ BRITISH (REDUCED)]

The first tribe of the Brachyura, the _Dromiacea_, comprises a number of Crabs that in arded as the aris_ (Plate IX), a furry, clu Crab, occasionally found on our southern coasts, has the last two pairs of legs short and carried up over the back, where they are used for holding a e which the Crab uses as a cloak to protect and conceal itself At the sides of the abdoed in between the telson and the last somite, a pair of ses of the uropods These are wanting in the other tribes of the Brachyura

[Illustration: _PLATE X_

_Calappa flammea_, BRAZIL (REDUCED)]

The _Oxystomata_ (Plate X), which foruished by the form of the ular instead of square in outline

The passages through which the water passes out froills, which in other Crabs open at the front corners of the mouth-frame, are carried forwards to the front of the head The Oxystomata are most abundant in tropical seas, but are represented on the British coasts by species of _Ebalia_, sravel a Crabs fornatha_, in which the mouth-frame and the maxillipeds that close it are more or less quadrilateral in shape The tribe is divided into two subtribes, which eneral shape of the carapace In the _Brachyrhyncha_ this is generally rounded or square-cut in front, without a projecting rostrureat majority of Crabs The Edible Crab and the Shore Crab (Plate IX) are familiar examples In the _Oxyrhyncha_, on the other hand, the carapace is generally narrowed in front, with a projecting rostrum, either simple or forked, and is often ared Spider Crabs, several species of which are common on our coasts The Giant Spider Crab of japan (Plate XI) is the largest of living Crustacea

[Illustration: _PLATE XI_

THE GIANT japANESE CRAB, _Macrocheira kaempferi_, MALE THE SCALE OF THE FIGURE IS GIVEN BY A TWO-FOOT RULE PLACED BELOW THE SPECIMEN