350 Puget Sound Marine Sta. Pub. Vol. 1, No. 30 



Tribe Anomura 



KEY TO FAMILIES 



A. Crab-like species. 



B. Antennae usually as long as the chelipeds ; last pair of trunk legs 



placed over the carapace. porcellanidae (p. 350) 



BB. Antennae not as long as the chelipeds; last pair of trunk legs 



not placed over the carapace. lithodidae (p. 351) 



AA. Shrirap-like species. (Not included in this paper.) 



Family PORCELLANIDAE 

 Genus Petrolisthes 



1, Petrolisthes eriomerus Stimpson. flattopped crab, porcelain crab 



(fig. 4) 



Rostrum or interantennal area rounded, bent slightly downward with 

 median ^oove; antennae without setae, very long, in some instances 

 twice the length of the carapace or the same length as the cheliped. Cara- 

 pace flattened, slightly longer than wide; surface quite smooth or with a 

 few very slight depressions and elevations, in some quite spotted, in others 

 marked with more or less irregular broken transverse lines, usually two 

 little bluish spots on either side of the median line near the posterior end. 

 Maxillipeds large, joints very irregular and much flattened, inner mar- 

 gin fringed with long silky hairs which are most abundant on dactyl and 

 propodus; ischium with a sharp spine-like projection on the outer side of 

 distal end; merus lobed at middle of inner side; carpus and propodus 

 convex on inner side. Chelipeds verj?^ large for size of carapace; hand 

 triangular; inner margin of dactyls smooth but distal ends sharp and 

 beaked; dorsal surface slightly roughened; carpus elongated and roughened 

 by a row of teeth on the outer edge which project anteriorly; merus with 

 rounded projection on the inner distal surface. First three pairs of walk- 

 ing legs somewhat hairy; merus quite flattened. Fifth pair of walking 

 legs rudimentary, folded up over the carapace. Color greenish brown 

 flecked with reddish brown spots on carapace and chelipeds ; chelipeds 

 and portions of carapace often bluish. First 3 pairs of walking legs 

 banded wath light gray markings. 



It is found on rocky shores at extreme low tide under rocks, crowded 

 down among finely broken pieces of rocks, barnacles and shells. Abundant 

 on northeast corner and south end of Brown Island (8) ; also at Newhall's 

 dock (5) and at all the rocky points between the Station (5) and Friday 

 Harbor (i) docks; found in 25 fathoms off Canoe Island (16). 



