1000 NODULARIA 
indications of rays; teeth very greatly compressed; muscle 
scars shallow; nacre bluish, brilliant and iridescent behind. 
Length 40, height 21, diam. 16 mm. 
Cochin-China; Siam; Cambodia. 
Unio ingallsianus Lea, Tr. Am. Phil. Soc., X, 1852, p. 282, pl. 
xxiv, fig. 41; Obs., V, 1852, p. 38, pl. xxiv, fig. 41—REEVE, 
Conch. Icon., XVI, 1865, pl. xxv1, fig. 126. 
Margaron (Unio) ingallsianus Lea, Syn., 1852, p. 36; 1870, 
p-. 58. 
Nodularia ingallsiana SIMPSON, Syn., 1900, p. 816. . 
Oxynaia ingallsiana Haas, Con. Cab., Unio, 1910, pl. xvt, figs. 
3-4- 
This differs from NV’. pazii in the following slight characters: 
It is not so wedge-shaped when viewed from above; it is fuller 
at the basal inflation; it is more nearly equilateral and the nacre 
is more brilliant. I have seen only the type, which is smaller 
‘than N. pazii, while I have before me several specimens of the 
latter. It is quite probable that a sufficient amount of material 
would show that these two absolutely blend together. 
Group of Nodularia trompi. 
Shell small, subtrapezoidal, wider behind, slightly inflated, 
with a rounded posterior ridge; beaks full, sculpture not 
seen; surface covered with very fine, nodulous, somewhat zig- 
zag corrugations, with upcurved posterior ridges on the pos- 
terior slope; epidermis reddish-brown or black; hinge-teeth 
compressed; pseudocardinals vertically striate. 
NopuLARIA TROMPI (Drouet and Chaper). 
Shell small, subrhomboid, narrower in front, convex, scarce- 
ly subsolid, inequilateral ; beaks apparently moderately full and 
not high; anterior end rounded, angled above; base nearly 
straight, inflated near the posterior end; dorsum slightly curv- 
ed; dorsal slope obliquely truncate; posterior ridge rounded, 
ending in a rounded point near the base of the shell; surface 
covered with fine, subnodulous sculpture, which is sometimes 
connected and zigzagged; dorsal slope sculptured with fine, 
