of the West Coast of North America. 3.95 



belief, will belong to it if it be retained bj carcinologists. 

 Of the other genera, Pachycheles^ PorceUana, and Polyonyx are 

 found on this coast. These genera are distinguished from 

 each other by well-marked characters : the first by its stout 

 rough chelipeds and short carpus ; the second by the long 

 narrow carapax, prominent front, and deep orbits ; and the 

 third by its broad carapax, and by the bi- or multiunguicu- 

 late dactyli of the ambulatory feet. The former character 

 distinguishes Polyonyx from Porcellanella (White). 



Most of the Pacific-coast species belong to the genus Petro- 

 listhes^ which is, moreover, by far the largest section of the 

 old genus Porcellana. 



The total number of species here recorded is sixteen, nine 

 of which I believe to be new ; twelve belong to Petrolisthes 

 (including Pisosoma) , two to Paehycheles, one to Porcellana 

 as restricted by Stimpson, and one to Polyonyx. 



I have examined specimens of all the species except Petro- 

 listhes gracilis J eriomerus^ and occidentalis. 



All the presumably new species here described are from 

 either the east or west coast of the peninsula of Lower Cali- 

 fornia, a district which has not as yet been thoroughly 

 explored for its marine fauna, although large collections of 

 birds, fishes, echinoderms, and alcyonarians have found their 

 way thence to the museums of the eastern States. 



Genus Peteolisthes. 



a. Carapax flat, ovate ; carpus at least twice as long 

 as wide. 



Carpus three times as long as wide ; anterior and 

 posterior margins parallel, straight, and 

 smooth, with a sharp tooth at posterior distal 

 end P. gracilis. 



No teeth in front of carpus, but a prominent inner 

 lobe and a tooth at posterior distal end ; 

 front triangular, depressed P. rupicolus. 



Front less prominent than in the last species ; no 

 prominent inner lobe to carpus ; posterior 

 margin of carpus denticulated P. eriomerus. 



Carpus with two or three teeth in front and a 

 tooth at posterior distal end ; dactylus of 

 larger cheliped strongly hooked ; all the limbs 

 fringed with long setse P. hirtipes. 



Postorbital tooth not spinous ; carapax covered 

 with short plications ; carpus with four blunt 

 teeth in front P. crentdattis. 



Postorbital tooth spinous ; a second spine behind 

 this, from which a ridged margin runs back- 

 ward ; carapax and chelipeds rugose P. occidentalis. 



Postorbital tooth obtuse, a spine behind it; carpus 

 with three acute teeth in front ; meros of 



