Stimpson, 1858
Carapace longer than broad. Dorsal surface very flat, depressed; regions not well indicated; absence of defined postero-lateral facet. Antero-lateral margins toothed or lobated behind the exorbital angles. Third maxillipeds: exopodite of a remarkable breadth and usually broader than ischium; merus articulated at distal outer angle; the suture between merus and ischium not oblique; palp articulating at the middle of the anterior border of merus. Chelipeds unequal; outer surface of chela often with a tuft of hairs near the base of fingers. Ambulatory legs without spinules on posterior border of merus; dactyli not flattened. (Guinot 1998)
Species treated:
Ptychognathus altimanus (Rathbun, 1914)
Ptychognathus barbatus (A. Milne Edwards, 1873)
Ptychognathus capillidigitatus Takeda, 1984
Ptychognathus glaber Stimpson, 1858
Ptychognathus hachijyoensis Sakai, 1955
Ptychognathus ishii Sakai, 1939
Ptychognathus takahasii Sakai, 1939