90 SMITHSONIAN MISCELI^ANKOUS COLLEICTIONS 



last pair of feet curved upward. The "hebdosternite," or last joint 

 of the sternum, is entirely covered by the base of the abdomen in the 

 male and nearly covered in the female. The male organs are large, 

 arising from the coxal joints of the posterior feet, and are concealed 

 beneath the abdomen, but they do not immediately enter the abdom- 

 inal appendages, being conducted to them in a depression of the ster- 

 num scarcely deep enough to be called a canal. The male abdomen 

 is very narrow except at the base, where it rather abruptly widens to 

 cover the last joint of the sternum and interjacent organs; the seg- 

 ments are all distinct, none soldered. 



This genus differs from Carcinoplax in its narrower carapax and 

 short chelipeds ; from Pscndorhomhila in its flattened dactyli. The 

 species are all inhabitants of the Chinese and Japanese seas. 



137. PILUMNOPLAX SULCATIFRONS Stimpson 



Pilumnoplax sulcatifrons Stimpson, Proc. Acad. Nat. Sci. Phila.. x. p. 93 

 [39], 1858. 



The following description was drawn up from a male; which, as it 

 happens, is the only male specimen of the genus met with during the 

 exploration : 



Carapax moderately convex in front, posteriorly flattened ; propor- 

 tion of length to breadth, i : 1.26. A slight longitudinal ridge or 

 angle on each side above and parallel with the postero-lateral margin. 

 The upper surface is naked and nearly smooth, not granulated ; the- 

 regions scarcely distinct. A curved sulcus extends somewhat irreg- 

 ularly from the depressed genital region to the lateral tooth. The 

 median frontal sulcus is rather deep, posteriori}^ bifurcating on the 

 pregastric region. Front broad, straight, little projecting, and 

 notched at the middle. The frontal margin is double, or divided by 

 a well-marked transverse sulcus. The antennary notches are deep. 

 Antennee naked, very slender, and nearly half as long as the carapax. 

 Antero-lateral margin very short, posteriorly continuous with the 

 postero-lateral ; it is four-toothed, including the angle of the orbit, the 

 third tooth largest and a little raised. I^atero-inferior regions con- 

 vex; horizontal suture deep. External maxillipeds smooth and 

 gloss}^ Chelipeds moderately large, smooth ; meros with a tooth 

 close to its superior extremity ; carpus lanose externally around base 

 of hand ; hand short, glossy ; fingers longer than palm, crossing at 

 the tips, moderately toothed within ; immovable finger margined 

 below with a slight crest exteriorly. Ambulatory feet smooth, long, 

 very slender, somewhat compressed and slightly hairy ; penult and 



