NO. 1205. SYNOPSIS OF THE NAIADES SIMPSON'. 849 



PARREYSIA HYPSIPRIMNUS von Martens. 



' r/o hypai^rimnua VON MARTENS, Besch. Deuts. Ost-Af., 1897, p. 230, pi. vn, 

 fig. l.i 



Lake Nyassa. 



(Group of Parrtysia molleuri.) 



Shell subquadrate, solid, inflated, rounded in front, truncated behind, 

 with high beaks, the sculpture of which was not observed, and a strong, 

 sharp, curved posterior ridge; surface concentrically grooved; pseudo- 

 cardinals thick, short, cut up with vertical grooves; laterals curved; 

 nacre white. 



PARREYSIA MOLLEURI Morlet. 



*Unio molleuri MOKLET, Jl. de Conch., XXXIX, 1891, p. 242, pl.-vu, fig. 4. 

 Valley of the Mekong River. 



Subgenus AURORA Simpson, 1900. 

 (Type, I'nio aiirorens Hemle.) 



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 having one or more strong, concen- 

 tric ridges, the posterior .slope being radiately ridged and nodulous; 

 epidermis fulvous, beautifully and delicately green radiated; pseudo- 

 cardinals conical, truncate, striate; laterals lamellar; nacre orange. 2 



PARREYSIA AUROREA .Heude. 



* Unio auroreus HEUDE, Conch. Fluv. Nank., VIII, 1883, pi. LVII, fig. 106. 

 *PJETEL, Conch. Sam., Ill, 1890, p. 145. 



China. 



Subgenus PSETTDOBAPHIA Simpson, 1900. 

 (Type, Unio biesianus Heude.) 



Shell large, oval, inflated, gaping in front and behind, rather solid, 

 with full beaks, the beak sculpture not seen, posterior part distinctly 

 biangular; ligament large; epidermis smooth, brownish, somewhat 

 rayed, right valve with a large, irregular pseudocardinal in front of the 

 beak, with a pit in front of it; behind it on the hinge are numerous 

 denticles, and at some distance behind two very faint laterals; left valve 

 with two large pseudocardinals, one behind the other, and two remote 



'Iain not positive as to the systematic position of this and the last two species. The 

 figure of the latter is from a very badly eroded shell, and it is difficult to tell what its 

 affinities are. 



-Heude's brief Latin description so poorly describes the peculiar species placed 

 here that I can not be sure where it belongs, and that it should not have generic 

 rank. I place it here provisionally. 



Proc. N. M. vol. xxii 54 



