980 NODULARIA 
An abundant, variable species widely distributed through 
southeastern sia. I have united a number of nominal species. 
not being able to satisfactorily separate them. ‘The species 
is usually rather thin or barely subsolid, and more or less 
tinted with blue; the surface is almost always dull, the nacre 
brilliant and bluish. Unio evitatus of Lea is generally a little 
higher and more compressed than the type; U. humilis of Lea 
is a small form and might possibly be worthy of varietal rank 
if there was not so much intermediate material. Unio ander- 
sonianus Nevill is probably a synonym. U. gerbidoni Eydoux 
seems from the figure to be a rather solid cerulea. 
NopDULARIA SUBSTRIATA (lL,ea). 
Shell small, elongated, subinflated, scarcely subsolid, inequi- 
lateral; beaks full, rather high, apparently sculptured with a 
few irregular nodules: anterior end rounded, subangular 
above; base line nearly straight to a decided swelling behind 
the middle, obliquely truncated behind the swelling; posterior 
ridge somewhat double. ending in a point at or above the 
median line; surface ashy-greenish, dull; teeth delicate, lamel- 
lar; muscle scars shallow ;-nacre brilliant bluish-silvery, irides- 
cent behind. 
Length 26, height 13, diam. 9 mm. 
Siam. 
Unio substriatus Lea, Pr. Ac. N. Sci. Phila., VIII, 1856, p. 
93; Obs., VI, 1857; p.'20, pl: xxva, fig. 14. 
Margaron (Unio) substriatus Lea, Syn., 1870, p. 47. 
Unio subtriatus Léa, Jl. Ac. N. Sci. Phila., III, 1858, p. 300, pl. 
EXVL, hora. 
Nodularia cerulea (part) Simpson, Syn., 1900, p. 811. 
In the Synopsis I placed this in the synonymy of NV. cerulea, 
but the type, the only specimen I have seen, differs in some 
minor characters. It is a small shell, though no smaller than 
other specimens before me, which I believe are genuine ce- 
rulea, and it is possibly a little more elongated than shells of 
that species of its size. The beaks are slightly eroded but 
their sculpture occupies a less area than in cerulea and appears 
to be more granulous or nodular. 
