118 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.47. 



peds equal, much more massive than the legs. In both sexes all seven 

 abdominal segments are distinct and in the male the third segment 

 covers the whole width of the sternum between the bases of the last 

 pair of legs. 



This genus is closely related to Carcinoplax ^ of the Indo-Pacific 

 region, but differs chiefly m the form and disposition of the maxil- 

 ipeds, the separation of the front from the orbit, and the presence of 

 striduiating apparatus. 



TRIZOCARCINUS DENTATUS (Rathbun). 



Plate 1. 

 Carcinoplax dentatus Rathbun, Proc. U. S. Nat. Mus., vol. 16, 1893, p. 243. 



Type-locality.— GuU of Cahfornia, lat. 29° 40' N.; long. 112° 57' 

 W., 76 fathoms, green mud, temperature 59° F., station 3016, U, S. 

 Fisheries steamer Albatross. 



Type.— Ca,t. No. 17462, U.S.N.M. 



Distribution. — Gulf of Cahfornia, 30 to 76 fathoms, green and gray 

 mud, temperature 59° to 62° F. 



The striduiating ridge on the pterygostomian region is crossed by 

 about 70 fiiie strise. A short, complementary ridge exists on the 

 lower proximal margin of the inner surface of the arm and is crossed 

 obliquely by 10 or 11 strise. 



Subfamily PRIONOPL.A.CIN'JE:. 



CYRTOPLAX,2 new genus. 



Type of the genus. — Cyrtoplax spinidentata (Benedict). 



Carapace much broader than long, convex longitudinally and 

 transversely. Regions well marked. Antero-lateral margins arcu- 

 ate, dentate; postero-lateral margins converging. Fronto-orbital 

 width three-lifths of width of carapace. Front advanced, lobes arcu- 

 ate, separated only by a furrow from the orbital margin. Eyestalks 

 tapering, corneas small. Basal joint of antemia rather Avide, inner 

 angle just touching the front; flagellum standing in the orbital hiatus. 

 Buccal cavity widening distaily; maxillipeds gaping, merus broader 

 than long. Chelipeds stout, unequal, wrists subtriangular in dorsal 

 aspect, bispinose; palms high, fingers strongly deflexed. Legs long 

 and slender; dactylus of last pair upcurved. The first and third 

 abdominal segments of the male do not cover the sternum; the third* 

 fourth, and fifth segments are fused. 



This genus is much further removed than Eucrotopsis from the 

 Xanthid genus Panopeus. The carapace is much broader than in 

 Eucratopsis, the eyestalks are slenderer, the eyes smaller, and the 

 base of the male abdomen wider, but the first segment does not cover 



1 Milne Edwards, Ann. Sci. Nat., ser. 3, vol. 18, 1852, p. 164 (128). 



2 Kupids, convex; izUi, anything flat and broad, carapace. 



