396 Mr. W. N. Lockingtoii cm the PorceUanidea 



ambulatory feet with two or three spines on ^ 



upper edge, and one at posterior distal end . . P. armatus. 



Pre- and postorbital spines acute ; front boldly 

 triangular, a spine behind postorbital ; carpus 

 spinous before and behind ; chelipeds equal ; 

 meros of ambulatory feet with a row of spines 

 anteriorly ; carapax and all the limbs pubes- 

 cent P- Edwardsius ? 



h, Carapax convex ; carpus short ; chelipeds stout. 



Carpus nearly twice as long as wide ; carpus and 

 manus with three longitudinal rolling ridges ; 

 chelipeds equal P. sinuimamis. - 



Carpus as broad as long, front margin laminate ; j-'"" 



hands flat ; chelipeds subequal P. gihhosicarpus." 



Hands dissimilar ; carpus nearly as broad as long, 



its laminate front margin with three crenu- . - ' ' 

 lated teeth P. setimanus. 



Carpus as broad as long ; front lamina in three 

 low lobes ; carapax and chelipeds smooth and 

 shining ; a white spot behind each eye on ^ 



antero-lateral margin P. biocellatus. 



Genus Pachycheles. 



Carapax with a raised margin, front entire ; 

 chelipeds very unequal ; carpus very short, 

 not toothed in front; manus protuberant „ 



along the centre P. rudis. 



Carapax and limbs with long pubescence, front 

 trifid ; chelipeds equal, with large tubercles 

 above ; carpus with a single large lobular 

 tooth in front P. tuberculipes. 



Genus POKCELLANA. 



Carapax exceedingly elongate ; postorbital acute, 

 a spine on antero-lateral margin behind ; 

 chelipeds subequal ; a small spine in front of 

 carpus P- transversilineata. 



Genus POLYONYX. 



Carapax and limbs smooth ; chelipeds equal ; 

 carpus with a deep concavity in front for the 

 manus ; dactyli of ambulatory feet multi- 

 unguiculate P- nitidus. 



Petrolisthes gracilis, Stimpson. 

 Petrolisthes gracilis, Stimpson, Ann. Lye. Nat. Hist. vii. p. 74. 



I have not examined any specimens which answer to 

 Stimpson's description of this species. 



Petrolisthes rujyicolus, Stimpson. 



I'etroliithes rupicolus, Stimpson, Prodr. des Anim. ^vert. p. 65. 



This species appears to have a wide range. To the south 

 it extends along the west coast of Lower California (Asuncion 



