1900.] A. Alcock — Carcinological Fauna of India. 407 



Ptxidognathus, A. M. Edw. 



Pyxidognathus, A. Milne Edwards, Bull. Soc. Philom. Paris (7) II T. 1878, 

 p. 109 : de Man, Notes Leyden Mus. V. 1883, p. 160, and Journ. Linn. Soc, Zool., 

 XXII. 1888, p. 148. 



Hypsilograpsus, de Man, Notes Leyden Mus. I. 1879, p. 72 (ipso teste). 



This genus is closely related to Varuna and Ptychognathus. It 

 differs from Varuna in the same particulars that Ptychognathus does, 

 that is to say, the exognath of the external maxillipeds is much broader 

 than the ischiognath, and the dactyli of the legs though compressed 

 are not dilated. It farther differs, both from Varuna and Ptychognathus 

 in the following characters : — 



(1) the carapace is decidedly transverse, is deep, and is dorsally 

 strongly convex in both directions : it is also anteriorly declivous with 

 the front deflexed, and its antero-lateral borders are hardly arched : 



(2) the anfcennules fold transversely : 



(3) the lower border of the orbit is complete, except of course at 

 the orbital hiatus : 



(4) the carpopodites and propodites of the legs are not particularly 

 broad. 



Distribution : Indo-Pacific in fresh or brackish water. 



Key to the Indian species of Pyxidognathus. 



I. A single spine on the posterior border of the meropodites 



of the legs P. fiaviatilis. 



II, More than one spine on the posterior border of the mero- 

 podites of the legs P.deianira. 



95. Pyxidognathus deianira, de Man. 



Pyxidognathus deianira, de Man, Journ. Linn. Soc, Zool., XXII. 1888, p. 148, 

 pi. x. figs. 4-6. 



Carapace about § as long as broad, convex, smooth, without 

 distinction of regions excepting a faintish H-shaped mark in the 

 middle. Free edge of front sinuous or four-lobed, as in the next species. 



Antero-lateral borders of the carapace cut into three prominent 

 acute teeth (including the outer orbital angle), the first of which is the 

 largest, and the last of which is spine-like. 



Upper border of orbit slightly sinuous, lower border finely denti- 

 culate. 



Exognath of the external maxillipeds, in the male, very much 

 broader than the ischiognath, and having a smooth convex surface. 



Chelipeds in the young male about If times the length of the cara- 

 pace : inner border of ischium, arm, and wrist denticulate ; inner angle of 

 J. ii. 53 



