ALLORCHESTES. 39 



The inferior antennae have the basal articulation not 

 so closely fused with the head as in Orchestia, and a 

 small olfactory denticle is visible. The foot-jaws ter- 

 minate in a sharp curved nail. The hands of the first 

 two pairs of legs are subchelate in both sexes. The an- 

 terior pair are small, the second are generally large and 

 powerful in the male. In the female, though occasion- 

 ally smaller than those of the male, they are never rudi- 

 mentary, and are generally developed upon the type of 

 the male, except that the wrist is produced along the 

 inferior margin of the hand. The first joint (or coxa) of 

 the first four pairs of limbs is large and squamiform, being 

 nearly as deep as the body of the animal. The first joint 

 of the fifth pair of legs is much shorter than that of the 

 preceding pairs. The caudal appendages are short and 

 stout, the posterior being unibranched. 



In habits as well as in organization, Allorchestes occu- 

 pies a position between Orchestia and Gammarus. It is a 

 littoral genus, dwelling generally under weed upon the 

 shore, and in pools left by the sea. One species only, 

 A. medius, is recorded by Dana as having been taken by 

 the dredge in two separate localities, in several fathoms 

 of water. 



The geographical range of this genus is very wide. 

 It is found throughout the temperate and subarctic 

 zones of both hemispheres. 



Under the name of Enone Risso has described (Eu- 

 rope meridionale, p. 96) a genus which we believe to be 

 identical with the present; but the description is so des- 

 titute of distinctive characters, that it is not sufiicient 

 to warrant its acceptance even as a synonym. 



