402 Mr. W. N. Lockino;ton on the Porcellanidea 



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the anterior margin of the carpus ; in others they are small, in 

 others large and prominent. One specimen combines with tiie 

 want of these teeth a carapax the surface of Avhich is plicate 

 upon the margins. The rolling ridges of the manus and car- 

 pus, and the deeply punctate surface of both, are constant 

 characters. 



This species is intermediate between Petrolisthes proper and 

 Stimpson's Pisosoma^ the carapax answering to the latter, the 

 chelipeds approaching the former. 



Petrolisthes {Pisosoma) gihhosicarpuSj nov. sp. 



Carapax smooth, somewhat convex, becoming slightly 

 plicate on the postero-lateral margin, somewhat pentagonal, 

 antero-lateral angles rounded ; gastric and cardiac regions de- 

 fined by sulci ; front entire, sinuous ; postorbital tooth very 

 slender and acute. 



Flagella of antennge more than twice the length of the 

 carapax. 



Chelipeds subequal; meros with a laminate tooth at its 

 anterior distal end above, and a spine on the underside dis- 

 tally ; carpus as broad as long, the anterior upper margin 

 entire, laminate, the lamina broadest near the proximal end ; 

 distal margin lobular ; manus flattened, narrower than carpus ; 

 fingers gaping but slightly; dactylus hooked at tip and crossing 

 the tip of the pollex. 



Surface of carpus and manus punctate above when viewed 

 with a lens, the carpus rugulose on its outer margin. 



Ambulatory feet set with long hairs, especially upon their 

 anterior surface, manus somewhat punctate ] no hairs or pu- 

 bescence on carapax or chelipeds. 



Length and width of carapax equal, each measuring six 

 millims. in the single female individual from which this species 

 is described. 



The hand and carpus show traces of decorative coloration, 

 having a central area surrounded by a darker band. 



The exact locality of my specimen is unknown ; but it cer- 

 tainly came from Lower California. 



From the comparative stoutness of the chelipeds and the 

 slight projection of the front, this species would appear to 

 belong to Stimpson's genus Pisosoma. 



Petrolisthes [Pisosoma) setimanus, nov. sp. 



Carapax orbiculate, regions circumscribed by sulci, that 

 behind the gastric region deepest. Postero-lateral regions 

 crossed by nigge. 



