CRL'STACE A XORTH PACIFIC EXPLORING EXPEDITION 129 



less depressed, the posterior portion being a little convex trans- 

 versely. The surface is somewhat uneven, but smooth and glabrous. 

 The gastric lobes are more prominent. Front broader, more in- 

 clined, and less projecting, with the median sinus broader and deeper. 

 The second lateral tooth is sharp, more projecting, and more widely 

 separated from the first or orbital angle. The infraorbital margin is 

 more coarsely crenated. In other respects it is like P. dcprcssus. 

 Dimensions of a male: Length of carapax, 0.42; breadth. 0.51 inch. 

 Proportion, i : 1.21. 

 Found at Loo Choo. 



Genus PTYCHOGNATHUS Stimpson 



Carapax flat above ; antero-lateral margins acute, emarginated. 

 Buccal area and maxillipeds very broad, but narrowed posteriorly. 

 Exognath of outer maxillipeds greatly developed, as broad as the 

 ischium of the endognath. No piliferous crest on the endognath ; 

 commissure of ischium and meros transverse ; meros not as long, 

 but twice as broad as the ischium, and very strongly auriculated at 

 the antero-external angle, the auricle being nearly as large as the 

 main body of the joint. Feet as in Pseudograpsus, etc. ; hand not 

 piliferous. Last joint of the sternum considerably exposed on 

 either side of the abdomen. Abdomen of the male rather narrow. 

 Terminal joint of female abdomen free. 



This genus is founded on a single species from the eastern seas, 

 which is remarkable for the flatness of its dorsal surface. It is 

 allied to Pseudograpsus and to Platygrapsus, but sufficiently dis- 

 tinct from both in the character of its outer maxillipeds, from the 

 former b}- the great breadth of these members, and from the latter 

 by the transverse commissure of the endognath. 



215. PTYCHOGNATHUS GLABER Stimpson 



Plate XVII, Fig. 5, 5a 



Ptxchoguafliits glaber Stimpson, Proc. Acad. Nat. Sci. Phila., x, p. 104 

 " [50], 185S. 



Carapax perfectly flat above, not at all deflexed anteriorly, and 

 very little sloped at the postero-lateral margins. Proportion of 

 length to breadth, i : 1.2 1. The H-shaped suture at the middle is 

 deeply impressed. Gastric lobules obsolete. Surface smooth, punc- 

 tate. Front broad, margin waved and grooved. Antero-lateral 

 margin bidentate, there being one slight emargination behind the 



