ORDER DECAPODA. 165 



being withdrawn altogether within their cavities, and whose 

 claws, in the males at least, are notably thicker than the 

 other feet. 



MiTHRAX, Leach. 



Their claws are very robust, with the fingers hollowed like 

 a spoon at the end. The stem of the lateral antennee is sen- 

 sibly shorter than the pedicle. The tail is composed of seven 

 articulations in both sexes. {Mitlirax spinicinctus, Latr.) 



ACANTHONYX, Latr., 



Have an advancement in the form of a tooth, or spine, at 

 the inferior side of the legs. The under part of the tarsi is 

 hairy, and, as it were, pectinated, and the upper part of the 

 testa is even. The tail of the males presents, at most, six 

 complete segments. {Meria glabra, Collect, du Mus. d'Hist. 

 Nat.) 



Pisa, Leach, 



Whose claws are of a middle size, with the toes pointed. 

 The legs have no spine underneath, and the tail consists of 

 seven segments in both sexes. As well as in the preceding 

 subgenera, the lateral antennae are inserted at an equal dis- 

 tance from the fossets, which receive the intermediate, and 

 from the ocular cavities, or more approximated to the latter. 



Some, as in the genus naxia of Dr. Leach, have two 

 ranges of denticulations under the tarsi, others have but a 

 single range of denticulations, or a simple fringe of thick 

 hairs in a knob, under the same articulation. Those which 

 are in this last case fonn the genus Lissa of the same. 



Among those which have but a single range of denticula- 



