132 
rounded : 9,nterior margin rounded^ or very obtusely angulated : 
umbo elevated : fosset behind the beaks, moderate, wider than 
long, not angulated behind : disk deeply wrinkled or undulated 
with a series of transverse elevations, sometimes separated by small 
longitudinal lines, so as to resemble, as it were, drops of a liquid, 
extending from the umbo to the base : within white : teeth direct. 
Length, about two inches and nine-tenths ; breadth, three 
inches and seven-tenths. Convexity, nearly two inches. Inhabits 
Wabash. 
A common species, distinguishable by the single series of trans- 
verse elevations on the middle. The allied species are U. cardice 
and incurvisj nob. *3 but besides other characters, it may be dis- 
tinguished from either by the less prominent nates, the smaller 
fosset, and the series of the disc. Amongst the numerous species 
sent to me by Mr. Barnes, previously to the publication of his 
paper, was a small valve of this species, but it was then referred 
as a variety to the convenient but obsolete receptacle of this 
genus, U. crassus. 
Unio velum. — Transversely elongate suboval, compressed, very 
fragile and thin, olivaceous, radiated with green ; umbo not 
prominent, placed far backward ; base subrectilinear ; anterior mar- 
gin more widely rounded in the posterior margin, with prominent 
membrane, crenate at its tip ; within margined with opake white ; 
primary teeth, a conic one in the left valve, with a recipient sinus 
in the right valve; lateral teeth simple and single in each valve. 
Length, more than half an inch ; breadth, less than one inch and 
one-fifth. Inhabits the Kentucky Biver. 
This pretty species is remarkable in having the epidermis ex- 
tended into a broad, crenate membrane, terminating the anterior 
margin. In the form of the teeth and the white interior margin 
this shell resembles the U. monodonta ; and, in fact, I was led 
from these characters to suppose it the young of that shell, but 
afterwards finding the young, and perceiving that the umbo was 
* I think these two species have long since been published under the 
names of cordata and intorta. I therefore suppress the descriptions here. 
I may remark, further, that the descriptions of Unio here given were 
chiefly made about three years since, together with nearly twenty others, 
which I suppressed, as the species were either anticipated or subse- 
quently made known in the works of recent naturalists » 
