1921 ] Schmitt: The Marine Decapod Crustacea of California 175 



Key to California Genera of the Porcellanidae ' 



I. Epimera (pleural, subbranchial, or lateral portions of the carapace) entire. 

 Chelipeds equal or subequal, broad and flattened; carpus more or less 

 elongated. 



Petrolisthes, p. 178. 



II. Epimera posteriorly broken up, the posterior portion of the subbranchial 

 region subquadrate and separated from the larger anterior portion by a 

 membranous or cutaneous interspace. Chelipeds unequal, thick, and more 

 or less roughened; carpus short. 



Pacliycheles, p. 175. 



Genus Pachycheles Stimpson 



Carapace rounded, ovate, at least as broad as long, with lateral margins marked 

 by an elevated line ; front somewhat deflexed, a little prominent at the middle, and 

 subacute, but never dentated, with its apex concealed by pubescence; epimera 

 posteriorly broken up, the posterior portion of the subbranchial region subquadrate 

 and separated from the larger anterior portion by a membranous or cutaneous 

 interspace. First or basal joint of antennal peduncle produced and joined to the 

 margin of the carapace; second joint at some distance from the orbit. Chelipeds 

 unequal, thick, and more or less roughened, carpus short. 



The species of this genus, listed below, in general appearance are all very much 

 alike ; the carapace is round-ovate ; front short, depressed, and pubescent ; cheli- 

 peds unequal, either the right or left the larger; carpus with two to three rows 

 of the granules more prominent than the rest; ambulatory legs more or less 

 pubescent on upper margin; propodi and dactyli spinulous below. 



Key to the California Species of Pachycheles 



I. Chelipeds rugose, granulated, and tuberculated above, and furnished with a 

 prominent, naked, granulated tubercle on the median distal portion of 

 the palm, near the gape of the fingers. Lateral (not terminal) plates of 

 telson in one piece. 



A. Chelipeds covered with a thick, dense, even, velvety pubescence, which 



also fills the gape between the fingers of the larger hand. (Santa 

 Monica Bay to San Diego.) 



holosericus, p. 177. 



B. Chelipeds with only a few scattered, coarse hairs on upper surface, and 



with only a few if any in the gape of the fingers. 



rudis, p. 176. 

 II. Chelipeds evenly rounded and not tuberculated above, quite uniformly granu- 

 lated; granules hidden beneath a short, thick pubescence, interspersed with 

 numerous tufts of longer hairs; gape between the fingers of the larger 

 hand filled with a dense, bushy pubescence. Lateral plates of telson com- 

 posed of two pieces, a small rounded proximal portion, and a large distal 

 portion which alone constitutes the lateral plate of the other species of 

 Pachycheles here listed. (Not found south of San Francisco Bay.) 



pubescens, p. 177. 



