1304 DIPLODON 



with a low wing, behind which it is bhintly, obhquely truncate 

 on the dorsal slope : anterior end rounded, subangulate above ; 

 base line curved, fullest behind the middle ; surface with finely 

 striated epidermis and showing in the middle of the disk a 

 few, subradial or oblique n^arkings ; teeth delicate, compressed ; 

 pseudocardinals double in the right valve and single in the 

 left ; laterals double in the left valve, single in the right ; nacre 

 bluish or purplish, rich and brilliant. 



Length 53, height t;j mm. 



Lagoon of the Lower Murray River. Australia. 

 IJyno (Alasmodon) eiansi Adams and Angas, Pr. Zool. Soc. 



Lond.. 1864, p. 39. 

 Unio e7'ansi Sowhri'-v. Conch. Icon.. X\'L 1867, pi. i.vi, fig. 



285. 

 Margaron (Unio) eiansi Lea. Syn.. 1870. p. 56. 

 Margaritana ciansi P.^iTEL. Conch. Sam.. IH. 1890, p. 173. 

 Diplodon cvansi Simpson, Syn., 1900, p. 892. 



A single young specimen labeled Unio evansi Adams and 

 Angas is in the Lea Collection without locality and it agrees 

 well with the original description of that species and with 

 Sowerby's figure of it. 



Section Cucumaria Conrad. 1853. 



Cucnniario Conrad. Pr. Ac. Nat. Sci. Phila.. VI, 1853, p. 269. 

 Cncumeria Simpson, Syn., 1900, p. 893. 



Shell elongated, trapezoidal, widest behind ; pseudocardinals 

 irregular, small, not well developed, showing a tendency to 

 break into denticles ; laterals feeble ; pallial line strongly pitted ; 

 nacre much thicker in front. 



Type, Unio nozfcc-hollandi<T (jray. 



Group of Diplodon novcc-hoUandi(r. 



Shell having the posterior two-thirds overed with irregular 

 nodules, which radiate somewhat from the posterior ridge. 



Dtpi.odon Nov.^i-HOIXANDPT: (Gray"). 



Shell much elongated, subcompressed or scarcely subinflat- 

 ed. rhomboid, somewhat solid; inequilateral, a little narrower 



