162 GENUS PAGURUS. [December. 



half as long as the thorax; this character, if constant, and 

 not a sexual difference, is very sufficient to distinguish 

 that from our specimen, in which the antennae are equally- 

 long with the thorax. In other respects this Hippa agrees 

 very well with the excellent detailed description of the H. 

 emerita, by Mr. Latreille, in the Hist, Nat. Crust, et Ins. 

 It may not be superflous to observe, however, that all the 

 descriptions 1 have seen of that species, with the exception 

 of the detailed one above-mentioned, represent the last 

 segment of the tail as oval; and although under the generic 

 head Mr. Latreille's words are, *' son dernier segment est 

 alonge, triangulaire," yet under die descriptions of spe- 

 cies, we have " Caudae ultimo scgmento ovato." 



Genus PAGURUS. 



Interior antennae short and bifid at tip: exterior ones 

 setaceous and longer; body oblong, thorax crustaceous; 

 abdomen vesicular, naked, soft and furnished at tip with 

 hooks or holders. 



SPECIES. 



1. P, pollicaris.'^ Thorax, with the first segment, 

 depressed, rounded and broader before; right ha?id larger, 

 granulate, almost tuberculate, subspinous above on the 

 wrist; thumb above elevated into a prominent angle, hand 

 dXidJinger crested and denticulated beneath. 



Inhabits the coast of the United States. 



Cabinet of the Academy. 



Anterior segment of the thorax subcordate, truncate 

 behind^ posterior segment gradually dilated to the base, 

 where it is emarginate for the reception of the abdomen; 

 small scales at the base above of the pedicels of the eyes 



