126 A HISTORY OF EECENT CRUSTACEA 



Family 2. — Matutidce. 



The characters are the same as in the Calappidas, ex- 

 cept that the third maxillipeds have the three terminal 

 joints concealed beneath the triangular acute fourth joint. 



The family contains four genera. 



Matuta, Fabricius, 1798, is regarded as the genus 

 among the Brachyura in which the adaptation for swim- 

 ming attains its highest development. In the last pair of 

 legs the oval terminal joint is supplemented by a very 

 broad expansion of the preceding joint. Moreover, the 

 other three pairs of legs are natatorial, having broad flat- 

 tened joints, in particular the pair next the chelipeds evi- 

 dently forming paddles of great power. Nevertheless, 

 none of these limbs are fringed with hairs, the ordinary 

 armature of swimming legs. The sufficient reason as- 

 signed for this is that the crab's safety often depends upon 

 the extraordinary rapidity with which it can bury itself 

 in the wet sand. Its flattened joints have sharp points 

 and edges, with the digging powers of which any fringe 

 of fur would seriously interfere. As it is, they can slip 

 themselves under the sand in a moment, and before the 

 troubled water has cleared over their departing footsteps 

 the traces of them are smoothed and lost. Yet sometimes, 

 it is said, their movements may be perceived under the feet 

 of a person walking along the shore. Among the Japanese 

 specimens of Matuta viator, Fabricius, de Haan observed 

 some of what he calls ' spurious females,' but he mentions 

 no peculiarities in them except their smaller size. If 

 Paulson's identification be right, the name of this species 

 should become Matuta lunaris (ForskSl.) 



Eepatus, Latreille, 1806, has, according to de Haan, 

 the third joint much shorter than the fourth in the third 

 maxillipeds, whereas in Matuta those two joints are equal 

 in length. Hepatus princeps (Herbst) appears to be the 

 proper name of the type species, which occurs both in the 

 East and West Indies. This genus, and with it Osachlla, 



