396 Mr. W. N. Lockington on the Porcellanidea 



ambulatory feet witli 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 ? 



b. Carapax convex ; carpus short ; chelipeds stout. 



Carpus nearly twice as long as wide ; carpus and 

 manus with three longitudinal rolling ridges ; 

 chelipeds equal P. sinuhnanus. 



Carpus as broad as long, front margin laminate ; 



hands flat ; chelipeds subequal P. gibbosicarpus. 



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 j 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. tubercuUpes. 



Genus Porcellana. 



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- 

 unguioulate P. nittdus. 



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 ruincolus, Stimpson. 

 Petrolisthes rupicohis, Stimpson, Prodr. des Anim. evert, p. 65. 



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

 it extends along the west coast of Lower California (Asuncion 



