94 SMITHSONIAN MISCELLANEOUS COLLECTIONS 



beneath white. Dimensions of the carapax in a male: Length, 0.16; 

 "breadth, 0.28 inch. 



It was dredged from a muddy bottom, in the "ten-fathom hole," at 

 Port Lloyd. Bonin Islands. 



Genus HETEROPLAX Stimpson 



This genus is allied to Carcinoplax in the character of the male 

 organs, and to Gonoplax in the shape of the carapax and the form 

 of the orbits. The carapax is trapezoidal, the facial region occupy- 

 ing nearly its whole width anteriorly. Front rather broad, notched 

 on either side at the insertion of the antennae. Eye-peduncles stout 

 and of moderate length. Antennae long and slender, the basal joint 

 movable, narrow, elongated, its outer apex filling the hiatus of the 

 orbit and nearly excluding the flagellum therefrom. Epistome 

 ample. Palatal ridge sufficiently distinct at the anterior buccal mar- 

 gin. External maxillipeds resembling those of Gonoplax, with 

 goniarthroid palpus. Chelipeds short, robust ; fingers oblique. Am- 

 bulatory feet slender, the third pair longest; dactylus compressed. 

 Abdomen of the male very narrow, but expanded at base so as to 

 cover the posterior segment of the sternum and reach the coxae of 

 the posterior feet. The virgulae, or male organs, arise from these 

 coxal joints, but reach the abdominal appendages through shallow 

 grooves on the sternum. 



The species are found on the coast of China. 



142. HETEROPLAX DENTATA Stimpson 



Hcteroplax dentata Stimpson, Proc. Acad. Nat. Sci. Phila., x, p. 94 

 [40], 1858. 



Carapax narrow, a little broader at the principal lateral tooth than 

 at the angle of the orbit. Proportion of length to breadth, i : 1.27. 

 Surface smooth and glossy; regions inconspicuous. Hepatic region 

 depressed. Antero-lateral and postero-lateral margins nearly con- 

 tinuous, the former very short, with four unequal teeth, the third 

 tooth much the largest and most prominent, placed at a higher level 

 than the second and projecting over it; fourth or posterior tooth in- 

 conspicuous, formed only by a slight emargination. Front straight, 

 somewhat bimarginate; no median notch. Eyes large. Chelipeds 

 short, smooth, and glossy; a small tooth near the summit of the 

 meros-joint and one at the inner angle of the carpus, and a tuft of 

 pubescence on the outer surface at the juncture of the carpus and 

 hand. 



