voeo2.” | PROCEEDINGS OF THE NATIONAL MUSEUM. 415 
part of the shell of which he speaks. A fine male example belonging 
with the type exhibits almost nothing of this expansion. Four of his 
specimens are rather more inflated than anything I have seen of the 
other species I have placed in the synonomy, though scarcely more so 
than some subellipsis, while other examples which Mr. Lea has placed 
with this species can not be distinguished from rutilans or eriguus. As 
arule, exriguus, which was described from a young specimen, is not quite 
so wide as rutilans, but there is inthe material I have examined every 
possible variation in width. 
U. subellipsis is generally somewhat solider than the other forms, 
but there is every grade in Lea’s suite, to shells of the most fragile 
character. In Florida the species seems to become smaller, the epidermis 
is often a tawny or brownish color, slightly rayed, and the shells are 
hardly so wide as the typical rutilans or modioliformis. One such a 
specimen, which is unusually dark, Dr. Lea named U. nigrinus, but on 
holding it up to the light it is seen to be distinctly rayed with green 
and yellow. U. Averilli is the same thing, but more brilliant in color. 
The Florida form is quite commonly sent out as U. floridensis Lea, the 
latter being the thin southern form of U. anodontoides, and an entirely 
different thing. I have examined many hundreds of specimens of these 
shells from various localities in the Carolinas, Georgia, Florida, Ala- 
bama, and- Mississippi, and I feel certain that I am right in uniting all 
these under one species. Ihave before me examples from Lake Ashby, 
Florida, collected by B. H. Wright, and sent by him to the National 
Museum as U. Averillii; Lea’s type of nigrinus from West Florida; 
shells from St. Augustine, collected by C. W. Johnson, and from numer- 
ous other localities in the State,and they are certainly all forms of the 
more northern species. 
ROUP OF UNIO SUBANGULATUS. 
Unio subangulatus is a peculiar shell, rather wide-oval in outline, 
and brilliantly rayed with blackish green on ayellow or straw-colored 
eround. The posterior portion in adults is often much produced and 
quite pointed; the ventral region is very full, and the shell usually con- 
siderably inflated. It is placed with U. sparus and scitulus by Dr. Lea 
and probably groups with them; though they have the peculiarities I 
have noticed much less developed. They inhabit Tennessee, Alabama, 
Georgia, and Florida. 
Unio subangulatus Lea. 
(Plate Lvul, Fig. 1.) 
Unio silbangulatus Lea, Obs. m1, p. 47, Pl. x, Fig. 23, Oct. 2, 1840. Chattahoochee 
River Columbus, Ga.; Dr. Boykin. 
Lea’s types were young shells, as the one he figures is but 1 ineh in 
length and 1.7 inches in width, and do not show the great ventral inflation 
nor the development of the posterior point as older specimens do, The 
