eee PROCEEDINGS OF THE NATIONAL MUSEUM. 413 
Unio dariensis Lea. 
(Plate Lin, Fig, 2, Plate Liv, Fig. 1.) 
Unio dariensis Lea, Obs. ut, p. 84, Pl. xxvi, Fig. 61, Oct. 21, 1842. Darien, Ga.; J. H. 
Couper. 
Some of the specimens of this species are so greatly inflated and pos- 
sess such a strong posterior ridge that they would seem to belong to the 
crassidens group, and from these there is every gradation to forms which 
would undoubtedly be placed with U. complanatus. The nacre varies 
from silvery to dark purple, and the cardinals from compressed to trans- 
verse. A young shell which I refer to this species, labeled “ Florida,” 
and belonging to Mrs. Andrews, is before me. This and the allied spe- 
cies, so far as I know, have only been reported from Georgia. 
GROUP OF UNIO SPISSUS. 
In form the shells which I have placed in this small group are related 
to U. ochraceus and the species which belong with it, but they differ in 
being wider, and in having the epidermis and nacre more like that of 
obesus. U. splendidus has the form of Downiei, spissus, geminus, and 
the rest of the group, but in coloring approaches ochraceus. This assem- 
blage seems to naturally include a few species ranging from North Caro- 
lina to Florida, among which U. Downiei has been obtained at seyeral 
localities in the latter State. U. borealis Gray, of Canada, though per- 
haps a small form of luteolus, closely resembles in shape some of the 
species which belong here. 
Unio Downiei Lea. 
(Plate 1v, Figs. 1-3, Plate Lv1, Fig. 5.) 
Unio Downiei Lea, Obs. VII, p. 28, Pl. xxv, Fig. 91, July 6, 1858. Buck Lake, Satilla 
River, Ga.; T. C. Downie and J. Postell. 
A fine species, of which the Lea collection contains numerous examples 
from various localities. The Georgia specimens are quite solid and in- 
flated, with a peculiar lurid nacre, having a tint of purple something 
like that of Unio Jevwettii. 
Hight specimens of a unio from several localities in Florida are before 
me, which have been a veritable stumbling block to students and over 
which I have been greatly puzzled. Some of them have been received 
as U. Anthonyi, but they are not at all like that species in any respect. 
Others have been labeled U. Hinkleyi by collectors, and there is some 
resemblance in all of them to U. monroensis. One of these, belonging 
to Mrs. Andrews and collected by F. Rugel, in Florida, is as large as 
any of Lea’s specimens of Dovniei, but is thinner and wider and has a 
more purplish nacre. From this there is an unbroken series down to 
what seem to be adult shells not quite 15 inches in length and 25 in 
width, which are rather thin, are not greatly inflated, and have the 
nacre strongly violet tinted. I had thought some of these must be 
