U2 



1XVKRT1-:15J;ATE ANIMALS. 



The first pair of legs are developed into jiretty powerful nipping- 

 claws or cliehe, and one of thein is alw.n's much larger than the 

 other, and acts as a kind of phig, blocking up the entrance of the 

 shell when the animal is retracted within it. 



('. Bi-'icliiiiira. — The Decapod Crustaceans included in this tribe 

 are familiarly known as Cral)s, and they derive their name of Bradiy- 

 urii, (Gr. hracJtiia, short ; and oura, tail) from the rudimentary con- 

 dition of the abdomen. The abdomen, in fact, is not oidy extremely 

 short, Ijut it is always tucked up beneath the greatly developed ceph- 

 alothorax, so tliat it is not visiljle at all, except when the animal is 

 looked at from below (fig. 89). The Crabs have very various habits, 

 but they are mostly denizens of the sliore, hilling beneath stones or 

 sea-weeil, in cracks of rock, or in ]iools near the line of low-water. 

 Some of them, however, can swim with tolcraljle activity, and .some 



of them (the Land-crabs) even live 

 habitually inland. One group, that 

 of the " Pea-cral5s," is distinguished 

 by the singular habit of living semi- 

 jiarasitica.Uy within the shells of 

 bivalve Molluscs, ssuch as the great 

 horse-mussel or the oyster. 



T)ie young or larval vVab is ex- 

 ceedingly unlike the adult, and has 

 a long and well-developed abdomen, 

 thus approximating to the tyjie of 

 structure which is permanently re- 

 taineil in the Macrura. 



( )RriER Stomapdda. 



The Stoiua]>ol Cru.staceans are 

 nc.irly allieil to the Decapods, hut 

 tliey ha\'e six or eight pairs of legs, 

 .ind the gills are not placed in chani- 

 bci-s on the under surface of the 

 tlior.ax, but are usually .suspended 

 benc.nth the abdomen. They are 

 Fi- 00. .s'.,";».. ,«"«//., tliu L.iciisi- almost all marine, and the Locust- 

 Shrimp or Sqiiil}<( (fig. 90) may be 

 taken as the type of tlie order. In 

 mi-u is well ilevcloped, and its terminal 

 swinnuing-tail. Tlu^ front pairs of legs 

 arc attached to the first five i]airs (jf ab- 



