1 144 PTVCIIORTIYNCHUS 



Length 36, height 26, diam. 19 mm." (Haas). 

 Type locality, Hubei. Hunan, Central China. 

 Poreyss'ia limwncnsis Haas, Nachr. Deutsch. Mai. Ges., 1910, 

 p. 97; Conch. Cab.. Unio. 1912, pi. 30, fig. 9. 



Genus PTYCHORHYNCHUS Simpson, 1900. 



Ftycliorliynclius Simpson, Syn., 1900, p. 850. 



Shell elongate, elliptical, round in front, pointed behind, the 

 point being midway of the height of the shell, solid, slightly 

 inflated, with a faint posterior ridge; beaks rather low, sculp- 

 ture not seen ; the posterior slope sculptured with strong, up- 

 curved ridges, w^hich sometimes extend slightly on to the disk, 

 which is otherwise smooth and shining ; left valve with two 

 rather stumpy, roughened pseudocardinals and 1-2 somewhat 

 blurred, granulous laterals ; right valve with a single blunt 

 pseudocardinal, the hinge line in front of which is excavated, 

 and a curious blurred lateral, which is sometimes slightly split 

 up; beak cavities shallow; dorsal scars few; nacre whitish. 

 Animal unknown. 



Type, Unio pfisteri Heude. 



I have placed in this group a number of forms which seem 

 to be rather closely related and have given the group generic 

 rank, because I could not refer the species to any known genus. 

 All are oblong formis with dark epidermis, with more or less 

 plicate sculpture on the dorsal slope. The pseudocardinals 

 are solid and generally triangular, the laterals usually remote 

 and not strongly developed. 



KkY to species of PTYCHORHYNCHUS. 



Shell regularly long ovate or nearly so. 



Posterior ridge well developed, epidermis olive-green. 



P. pfisteri. 

 Posterior ridge low, epidermis blackish-brown. P. Iccvis. 

 vShell more or less long rhomboid. 

 Posterior ridge double, shell biangulate behind. 



P. niemvenhuisi, apiccUatnm. 

 Posterior ridge not double. 



Shell rather short. P. schomhurgiannm. 



Shell somewhat elongated, P. mnrinum. 



