10 [Feb. 



Desrriplio7is of new species of fresh water Shelh.* 

 By T. A. Conrad. 



t;nio. 



Z7. cultelliformis. Oblong, compressed, thin posteriorly, slightly thickened 

 anteriorly, contracted obliquely from beak to base; umbonal slope rounded, 

 ventricose; ligament and basal margins parallel; posterior margin slightly con- 

 tracted, oblique; extremity rather obtusely rounded; basal margin nearly 

 straight or slightly contracted ; epidermis olive-brown with strong concentric, 

 lines; within bluish-white; cardinal teeth oblique, compressed, disposed to be 

 double in each valve ; lateral teeth compressed, slightly arched. 21. \\. 



Local. Bogan river, Australia. 



TJ. Napeaensis. Oblong-suboval ; anterior margin regularly rounded; pos- 

 terior margin obtusely rounded and nearly direct, extremity acutely rounded, 

 situated but little above the basal line ; ligament and basal margins parallel ; 

 basal margin slightly contracted ; disk contracted obliquely from beak to base ; 

 umbo with irregular angulated wrinkled plicae concentrically arranged ; epidermis 

 blackish-brown, obscurely rayed towards the base ; within bluish-white, with 

 wax-colored stains ; cardinal teeth compressed, disposed to be double in each 

 valve. 1|. \{. 



Local. Napean river, Australia. 



Z7. Balonnensis. Suboval or somewhat trapezoidal ; disk contracted from beak 

 to base; posterior side inflated ; posterior margin obliquely truncated, extremity 

 acutely rounded and much above the line of the base ; ligament and basal margins 

 parallel ; basal margin nearly straight in the middle ; umbonal slope rounded ; 

 posterior submargin with transverse wrinkled lines ; epidermis olivaceous, 

 strongly lined concentrically ; within white; lateral teeth compressed; cardinal 

 teeth elongated, compressed, very oblique, single in each valve, or slightly dis- 

 posed to be double in the right valve. 



Local. Balonne river, Australia. 



The posterior slope in two specimens is furnished with transverse wrinkled 

 prominent lines, but this does not appear to be a constant character of the spe- 

 cies. 21. li. 



TJ. Aberti. Suboval, much compressed, contracted from beak to base ; posterior 

 margin truncated, direct ; basal margin contracted posteriorly; beaks submedial ; 

 umbonal slope prominent or ridged, rounded ; middle of disk with irregular plicas, 

 running from umbo to base, becoming obsolete at base ; posterior slope with 

 w^rinkled lines and small plicae; epidermis olive-yellow, with small, very nume- 

 rous green dots, and a few broad rather indistinct rays ; within pale pink ; car- 

 dinal teeth thick, direct. IJ. If. 



Local. Chambers' Ford, rapids of Verdigris river, Arkansas. Dr. Wood' 

 house. 



Dedicated to Col. J. J. Abert. 



PALUDINA. 



p. svblineata. Ventricose-conoidal ; subumbilicated ; volutions 5, somewhat 

 * Received by the Academy in exchange from the Australian Museum. 



