eee PROCEEDINGS OF THE NATIONAL MUSEUM. 427 
yellowish brown, shining, with or without rays; usually rayless. Car- 
dinal teeth crenulate, oblique, single in the right valve, double in the 
left. “Lateral teeth short and straight; anterior cicatrices small, deep, 
not confluent; posterior cicatrices confluent, slightly impressed; nacre 
white, iridescent. A small creek near Palatka. The above is the 
original description. This seems to be perfectly distinct from U. mar- 
ginis, its nearest ally. Its smooth epidermis which, in all the speci- 
mens I have seen, is very light colored, even to yellowish, and the 
peculiar truncation of the anterior end, like U. coruscus, are its strong- 
est characters. It is an undoubted member of the parvus group. 
Unio papyraceus Gould. 
(Plate Lxviul, Fig. 2.) 
Unio papyraceus Gould, Proc. Bost. Soc. Nat. Hist., vol. mu, p.53* Aug. 20, 1245, 
Everglades. 
There arein the Museum collection two trays containing seven speci- 
mens of this species given to Mr. Lea by Dr. Gould, labeled ‘ Ever- 
glades, Cape Florida.” Part of them have been stained a brownish 
tint by coloring matter in the water; the others are olive to ash, with 
greenish rays. They are as fragile as Anodonta imbecillis, and Gould 
compares them to A. Couperiana, but the form and external coloring, as 
well as the bluish nacre becoming richly iridescent posteriorly, are al- 
most exactly like U. amygdalum, from which they seem to differ only in 
_ being more fragile. 
Unio trossulus Lea. 
(Plate Lxvint, Fig. 3.) 
Unio trossulus Lea, Obs. Iv, p. 36, pl. xt, Fig. 6. Aug. 18, 1843, Lake Monroe. 
This species is quite different from U. parvus, the type of the group, 
but is related by amygdalum and vesicularis to minor, which is near to 
parvus. I have seen but one specimen of the present species, Lea’s 
type, which is a somewhat peculiar shell, resembling in some respects 
the smaller, brighter forms of amygdalum, but it is more oblique and is 
quite small, being only 1.4 inches in width by 0.7 inchin length. It has 
the undulate beaks common to the group, as well as the silvery and irides- 
cent nacre, but is remarkably solid, with rather strong, subcompressed, 
ragged cardinals and heavy roughened laterals. 
GROUP OF UNIO CAMPTODON. 
Wide, large, somewhat quadrate or rhomboid shells, of rather light 
structure; without well-defined posterior ridge; with epidermis vary- 
ing from smooth, shining, and yellowish, to squamose, rough, and black. 
The nacre in the type is white, but it is often lurid or purplish in some 
of the species. The members of the group range from Virginia to 
South Florida, and west to Kansas and Texas. 
