Notes on North American Crustacea. 221 



the northern and southern varieties of this species, which 

 ranges from Cape Cod to Rio Janeiro. It is also found on the 

 west coast of America, as we have received an unmistakable 

 specimen from Mr. Xantus, collected at Cape St. Lucas. This 

 circumstance throws a doubt upon tiie distinctness of L. helli- 

 cosa, described in our last number. 



Acheloiis. 



A genus founded by De Haan. He refers to it but one 

 species, the Portunus spinimanus of Latreille. This species has 

 been placed in Lujpa by subsequent writers, but it appears to 

 be quite distinct in its narrower and pubescent carapax, its 

 anteriorly-produced meros-joint of the outer maxillipeds, and 

 its narrow dactyli of the ambulatory feet. "We have, there- 

 fore, found it necessary to retain the genus, and to place in it 

 several species usually referred to Amphitrite^ a heterogeneous 

 group of De Haan's, in which he placed L. gladiator^ hasta- 

 toides^ diacantha, and, with a query, crihraria, ruhra, and 

 pelagicus of Bosc {sayi Gibbes). This genus can scarcely be 

 retained, even were its name acceptable, which it is not, being 

 pre-occupied. 



The genus Achelous, as now constituted, is chiefly charac- 

 terized by the shape of the meros-joint of the external maxilli- 

 peds, which is greatly produced anteriorly beyond the base of 

 the palpus, with its outer margin usually straight, but some- 

 times a little projecting at the antero-exterior angle. The 

 carapax varies considerably in width, and in the length of the 

 lateral spine or posterior antero-lateral tooth. The terminal 

 joints of the first three pairs of ambulatory feet are sulcated, 

 and usually narrow, but sometimes rather broad and flattened, 

 although never approaching so much as those of the true swim- 

 ming Lupas. 



All the American species (except Ztcj)a rubra) usually 

 referred to Arnphitrite are here included. Tiie East Indian 



