PTYCHORHYNCHUS II45 



Group of Ptychorhynchus pUsteri. 

 Characters as in the genus. 



Ptychorhynchus pFisteri (Heude). 



Shell almost evenly long- elliptical or long ovate, convex or 

 subinflated, rather solid, inequilateral ; beaks but slightly ele- 

 vated ; posterior ridge well-developed, subangular or narrow- 

 ly rounded, ending behind in a blunt point on the median line ; 

 surface of the disk nearly smooth, exhibiting a few feeble, 

 low, concentric ridges ; posterior slope everywhere covered 

 with strong, corrugated plications ; epidermis shining, olive- 

 green ; pseudocardinals two in the left valve and one in the 

 right, stumpy, nearly smooth and even in size; laterals remote, 

 rather feeble, two in the left valve and a partially double one 

 in the right; beak cavities shallow with a few, faint dorsal 

 scars ; muscle scars but slightly impressed ; nacre whitish, iri- 

 descent behind ; pallial line with indications of a posterior 

 sinus. 



Length yy, height 34, diam. 20 mm. 



Nankin River, China. 

 Unio pUsteri Heude, Jl. de Conch., XXII, 1874, p. 112 ; Conch. 



Fluv. Nank., I. 1875, pi. i, fig. t. 

 Ptychorhynchus pfisteri Simpson, Syn., 1900, p. 851. 



This species bears some external resemblance to the North 

 American Ptychobranchus subtentus, but lacks the square blot- 

 ches. 



Var. inspiratum (Heude). 



Seems to differ from the type in having less sculpture on 

 the dorsal slope and the posterior point more drawn down. I 

 am doubtful whether it is worthy of varietal rank. 

 Unio pfisteri var. inspiratus Heude, Conch. Fluv. Nank., II, 



1877, pi. XIV, fig. 28. 

 Ptychorhynchus pUsteri var. inspiratus, Simpson, Syn., 1900, p. 



851. 



