PARKKYSIA 1 1 37 



Group of Parreysia molleuri. 



Shell subquadrate, solid, inflated, rounded in front, trun- 

 cated behind, with high beaks, the sculpture of which was not 

 observed, and a strong, sharp, curved posterior ridge; surface 

 concentrically grooved; pseudocardinals thick, short, cut up 

 with vertical grooves ; laterals curved ; nacre white. 



Pakreysia MOI.LRURI (Morlct). 



Shell subquadrate, solid, scarcely inflated, inequilateral ; dor- 

 sal outline very strongly arched throwing the rugose beaks 

 well up , anterior end a little narrowed, rounded ; base line 

 nearly straight ; posterior end almost squarely truncated ; pos- 

 terior ridge high, curved, angulate, ending in a blunt point at 

 the base of the shell ; surface covered with strong, concentric 

 striae; epidermis brown-green; pseudocardinals small, thick, 

 short, ragged ; laterals much curved ; nacre white. 



Length 25, height 21, diam. 14 mm. 



Valley of the Mekong River. 

 Unio molleuri MorleTT, Jl. de Conch., XXXIX, 1891, p. 242, 



pi. vir, fig. 4. — Haas, Conch. Cab., Unio, 1912, pi. 31, fig. 7. 

 Parreysia molleuri Stmp.son, Syn., 1900, p. 849. 



A peculiar form, somewhat quadrate in outline, strongly 

 arched on the entire dorsal region and altnost squarely trun- 

 cate behind. 



Haas, (1. c), considers this a synonym of P. fabagina. 



Subgenus Diaurora Cockerel!, 1903. 



Aurora Simpson, Syn,, 1900, p. 849. 



Diaurora CocKKRELr,, N'ant., XVI, 1903, p. 118. 



Shell small, ovate, subinflated, pointed behind, rather solid, 

 with high, small beaks and strong, corrugated sculpture, which 

 extends over half the disk in somewhat lachrymous, zigzag 

 ridges and nodules, the outer part of the disk apparently hav- 

 ing one or more strong, concentric ridges, the posterior slope 

 being radiately ridged and nodulous ; epidermis fulvous, beau- 

 tifully and delicately green radiated ; pseudocardinals conical, 

 truncate, striate ; laterals lamellar ; nacre orange. 



Type, Unio auroreus Heude. 



