NODULARIA 989 
Margaron (Unio) bonneaudi Lea, Syn., 1852, p. 32; 1870, p. 
50. 
Nodularia bonneaudi Simpson, Syn., 1900, p. 813. 
More rhomboid than N. cerulea or any of the nearly allied 
forms, and decidedly inflated. Looking at the shell from 
above, its greatest diameter is at the middle, decreasing very 
suddenly toward each end. According to Eydoux the beaks 
are not roughened. 
NODULARIA ASPERULA (Lea). 
Shell somewhat obovate, convex or subinflated, thin, inequi- 
lateral; beaks high and full; posterior ridge full, narrowly 
double, ending in a narrow biangulation about on the median 
line; anterior end rounded, angular above; base line lightly 
curved, quite full behind the middle; hinge line curved; dor- 
sal slope decidedly obliquely truncated; surface with faint, 
nodulous corrugations or almost smooth ; epidermis yellowish- 
green, sometimes having feeble, yellowish bands, with two or 
three dark green rays on the posterior end, shining; teeth 
very much compressed; pseudocardinals well developed; lat- 
erals curved; muscle scars shallow; nacre bluish, brilliant and 
silvery. 
Length 43, height 24, diam. 16 mm. 
Siam; Cambodia. 
Unio inornatus Reeve, Conch. Icon., XVI, 1865, pl. Xx1x, fig. 
147. 
Unio asperulus Vea, Pr. Ac. N. Sci. Phila., X, 1866, p. 133; 
jl. Ac. N. Sci. Phila., VI, 1868, p. 280, pl. xxxvui1, fig. 94; 
Obs., XII, 1869, p. 40, pl. xxxvui1, fig. 94. 
Margaron (Unio) asperulus Lua, Syn., 1870, p. 31. 
Nodularia asperula SIMPSON, Syn., 1900, p. 814. 
Oxynaia asperula Haas, Con. Cab., Unio, 1910, pl. xiv, fig. 5. 
Margaron (Unio) versus Les, Syn., 1870, p. 46. 
This species combines characters of the cerulea and contra- 
dens groups. The younger shells, which I have seen, would in- 
dicate close relationship to the former assemblage; adult 
specimens have characters of the latter. The species is not so 
elongated as cerulea or inornata and is more polished. 
