164 SMITHSONIAN MISCELLANEOUS COLLECTIONS 



Genus ONYCHOMORPHA Stimpson 



Carapax flat, unguiform, longer than broad, posteriorly broadly 

 expanded and laminiform, anteriorly narrowing. Front very short, 

 truncated, non-rostrate, and scarcely as prominent as the epistome. 

 Orbits very minute, deeply notched or fissured at the middle above, 

 and with a small hiatus within. Antennulary fossae oblique. Epi- 

 stome very small. External antennae obsolete. Buccal area longer 

 than broad. Anterior margins of pterygostomian channel entire. 

 Basal joint of outer maxillipeds very small ; exognath much broader 

 than endognath, with arcuated outer margin ; endognath very slen- 

 der, its apex projecting less far beyond that of the exognath than 

 in the other genera of this family; ischium- joint shorter than the 

 meros. Chelipeds much depressed, hand almost laminiform, fingers 

 very short, oblique, almost transverse. Sternum of moderate 

 breadth. Abdomen of the male subtriangular, broad and tumid 

 near the base, sides toward extremity a little concave, segments con- 

 fluent except at base and extremity. 



This genus is easily recognized by the great expansion posteriorly 

 of the carapax and the non-rostrate front. 



264. ONYCHOMORPHA LAMELLIGERA Stimpson 

 Plate XIX, Fig. 8, 8a 



Onychomorpha lamelligera Stimpson, Proc. Acad. Nat. Scl. Phila., x,. 

 p. 162 [60], 1858. 



Carapax almost laminiform, somewhat lyre-shaped, broadest at 

 the posterior extremity, narrowing anteriorly, and deeply sinuated 

 or contracted at , the level of the third pair of feet. Breadth tO' 

 length as i : i.i. Front very short; margin straight. Antero- 

 lateral and posterior margins somewhat curved, convex. Upper 

 surface glabrous, lightly convex about the middle, depressed and 

 faintly radiated toward the margins. Pregastric region depressed 

 below the level of the front. Outer maxillipeds and lower surfaces 

 of the body smooth. Chelipeds smooth ; meros trigonal but de- 

 pressed, with sharp edges ; carpus small, with acute exterior edge ; 

 hand much dilated, lamelliform, pubescent at inner edges and lower 

 surface ; fingers deeply sulcated, constituting one-fourth the length 

 of the hand. Ambulatory feet slender, with no laminiform expan- 

 sion; dactyli slender as in Cryptocnemiis pentagoniis. Abdomen of 

 the male with a sharp tooth at the extremity of the penult joint and 



