68 



41. PoTAMON (Acanthotrlphusa) calvum, Alcock. (Fig. 14.) 



This species is best defined by comparison with P. crenuli/erum, from 

 which it differs only in the following particulars : — 



The carapace is suborbicular in outline and is convex in all directions ; 

 all its regions are better defined. 



The front is more prominent, overshadows the epistome more, and 

 has its edge broadly bilolied. 



The anterior marginal tooth of the carapace is separated from the 

 outer orbital tooth by a wider gap, and in the gap there is usually a 

 bead-like tubercle. 



The three posterior marginal teeth are spines, not broad teeth. 



The epigastric crests are more tumid and more advanced, the post-orbital 

 crests are sinuous. 



The legs, though otherwise similar, are slenderer. 



In a large specimen the carapace is IrV inch long, 1-h inch broad, 

 and t'«tbs inch deep. 



.5520 5530 ,; ^, . t w .^ m f 10 c?, 8? 



— , Upper leiinasenm. J. Wood-Mason. -[ ,. , ,. , n 



10 10 I (including typesj. 



Although it looks so different, I am strongly inclined to regard this 

 species as merely a race of P. crenuUferum. 



42. PoTAMON (Acanthotelphusa) martensi, Wood-Mason. (Fig. 52.) 



['aralelphnm imiHensi, Wood-Mason, P. A. S. B., 1S75. p. 230 ; and Ann. Mag. Nat. Hist. (4), XVII., 1876, 

 pp. 121, 122. 



Potamoii{Par(Uelphusa) martensi, Mary J. Ralhhun, ^ouv. Archiv. du Museum (4), VII., 1905, p. 258, pi. 

 xii.. fig. 9 {iihi lil.). 



Carapace squarish, convex, its surface uneven but smooth, except for 

 some fine, short, faintish ripples near the postero-latei'al borders ; its length 

 al)Out three-quarters its greatest breadth, its depth half its length. 



Cervical groove well graven only where it defines the mesogastric area, 

 elsewhere superficial and very broad. All the regions are distinguishable, 

 and the small pair of prajcardiac facets are very distinct. The epibranchial 

 regions are transversely humped. The tip of the mesogastric area can 

 only just be discerned l)ehind the shallow groove that separates the 

 epigastric crests. 



Front moderately declivous, nearly two-fifths the greatest breadth of 

 the carapace in the adult, with convergent, slightly tumid sides, and broadly 

 bilobed edge. Upper border of orbit creased near the middle ; lower border 

 separated from the outer orbital tooth by a gap. 



Antero-lateral borders of carapace about as long as the postero-lateral, 



