22 University of Michigan 
This identification of the type has no effect if the species 
has been described satisfactorily in the meantime. Two names 
of Rafinesque, /ateralis and cordatus, should be considered first. 
The latter has been used for this species by Conrad and an 
excellent figure been given; the former has been referred here 
by Vanatta after examination of the so-called Rafinesque- 
Poulson “type.” 
Conrad’s use of cordatus is contradicted again by Vanatta, 
who says that the supposed type of cordatus is U. plenus Lea. 
But this does not agree with the original description and figure, 
which unmistakably indicate the so-called obliqua Lam. and 
cordatus of Conrad (736). It is a triangular, thick, swollen 
shell, with a sinus on the postero-inferior margin and a depres- 
sion upon the disk, with brown epidermis and white nacre. 
The outline of Rafinesque’s figure (6) expresses the character 
of a young “obliqua” very well, and his cordata was a young 
shell about one inch long. 
“The specimen in the Rafinesque-Poulson collection (No. 
20221, A. N.S.) is a characteristic Unio obliqua Lam., larger 
and less rayed than Conrad’s (Mon., pl. 25), but agreeing 
closely with it in form. Mr. Vanatta concurs in this determi- 
nation. He was formerly misled by some lots of the same 
form which had been carelessly labelled ‘U. plenus Lea.’” (H. 
AU res) 
On the other hand, Obl. lateralis Raf. is also this species. 
The description indicates a thick, swollen shell of oval, oblique 
shape, with an oblique, curved depression upon the disk, brown 
epidermis and white nacre, which is sufficient for its recogni- 
tion. Vanatta’s examination of the so-called Rafinesque-Poul- 
son “type” has confirmed this. 
Thus, there are two names available for this shell, lateralis 
and cordata, both recognizable from the original description, 
