1 290 DIPLODON 



Unio napca)iensis Conrad, Pr. Ac. N. Sci. Phila., V, 1852, p. 



10; Jl. Ac. N. Sci. Phila., 1854, p. 296, pi. xxvi, fig. 4. — 



— Rrrve, Conch. Icon.. XVI, 1865, pi. xxiii, fig. 2. 

 Margaron (Unio) napcanensis Lka, Syn., 1852, p. 20; 1870, 



p. 30. 



Distinguished by ils strong and peculiar beak sculpture, 

 which often extends one-third of the way over the disk and 

 by having the posterior end almost squarely subtruncate. The 

 epidermis is black and polished. The type of Unio dorsuosus 

 Gould, which is before me, is a young and light-colored speci- 

 men and napcanensis Conrad is the adult state of the same. 



DiPLoDON glen]5T.ge:nsis (Dennant). 



Glenelg River, Victoria. 

 Unio glenelgcnsis Dennant, Pr. Roy. Soc. Vict., X, 1898, p. 



112, pi. IV. 

 Diplodon glenelgensis Simpson, Syn., 1900, p. 889. 



The description of this species is not accessible to me and 

 I am therefore obliged to omit it. 



( J roup of Diplodon menzied. 



Shell subrhomboid ; beak sculpture not strong, consisting 

 of broken, nodulous ridges curving toward each other below, 

 with generally a smooth space between, not extending over the 

 .shell. 



xA.nimal as in the subgenus. 



Diplodon menziezi (Gray). 



Shell subelliptical or subrhomboid, conupressed, rather thin, 

 inequilateral ; beaks neither high nor full, having the charac- 

 teristic sculpture of the group; posterior ridge low and widely 

 rounded ; anterior end a little narrowed, rounded ; dorsal and 

 basal lines lightly curved, the latter often slightly fuller be- 

 hind the middle ; dorsal slope obliquely subtruncated or round- 

 ed ; surface with irregular, concentric sculpture, sometimes hav- 

 ing in addition faint, somewhat wavy, broken, radial sculpture ; 

 epidermis greenish-olive, dull or faintly shining ; teeth com- 



