FRESH WATER AND LAND SHELLS. Lal. 
trices nearly in the centre of the cavity of the beaks, on the inferior posterior part of the 
cardinal tooth; palleal cicatrices distinctly impressed; cavity of the shell shallow, cavity 
of the beaks shallow and subangular; nacre white and iridescent. 
Remarks.—It is to be particularly regretted that a single specimen only of this species 
should have been received from Dr.Gibbes. The cardinal teeth in both valves are tripartite. 
They are distinctly divided into three lobes, of nearly equal size and form. ‘This is so unique 
that I have inserted it with some hesitation as a permanent character, tripartition being 
so unprecedented. It may possibly be accidental. Should other specimens prove this 
form to be persistent, this species will present an anomaly peculiarly its own. The lateral 
teeth are, as usual, single in the right and double in the left valve; but the terminal in- 
ferior portion is remarkably enlarged and thickened in the latter valve, so as to run 
beyond the superior portion. The marginal portion of the disc is remarkably furnished 
with imbricate epidermal matter. It has somewhat the outline of U. complanatus, but may 
easily be distinguished from that species by its being more elevated in the beaks, in its 
imbricate margin, and in the form of the teeth. 
Unio perstriatus. PI. XII. Fig. 3. 
Testa levi, valdé transversa, valde compressa, subemarginatd, valdé inequilaterali, posticé subbiangulata; 
valvulis tenuibus; natibus parvis, vix prominentibus, ad apicem undulatus ; epidermide luteo-fuscd, perstriata; 
dentibus cardinalibus parvis, obliquis ; lateralibus prxlongis rectisque; margarita alba et iridescente. 
Shell smooth, very transverse, very much compressed, subemarginate, very inequilateral, subbiangular behind; 
valves thin; beaks small, scarcely prominent, undulated at the tip; epidermis yellowish-brown, very much 
striated ; cardinal teeth small, oblique; lateral teeth very long and straight; nacre white and iridescent. 
Hab. Abbeville District, S. C. J. P. Barratt, M. D. 
My cabinet and cabinet of Dr. Barratt. 
Diam. .5, Length 1, Breadth 2.3 inches. 
Shell smooth, very transverse, very much compressed, slightly emarginate, very inequi- 
lateral, subbiangular behind, obtusely rounded before, posterior slope wide and flattened ; 
substance of the shell thin; beaks placed near to the anterior margin and furnished with 
minute undulations at the tip, scarcely prominent, but rather pointed; ligament long and 
thin; epidermis yellowish-brown, with numerous imbricate stria covering nearly the 
whole of the disks, and with only one or two distant marks of growth; umbonial slope 
biangular and flattened; cardinal teeth small, oblique, double in the right and single in 
the left valve; lateral teeth very long, straight and thickened at the posterior ends; 
anterior cicatrices distinct; dorsal cicatrices placed under the plate between the cardinal 
and lateral teeth; cavity of the shell exceedingly shallow; cavity of the beaks very shal- 
low and rounded; nacre white and iridescent. 
Remarks.—Dr. Barratt sent me four specimens of this species, which may easily be 
distinguished by its peculiar striated epidermis, and its compressed form. It scarcely 
belongs to that large group of which the U. complanatus is the type, but certainly borders 
on it. The nacre of three of the specimens is white, slightly tinged with blue. The 
fourth specimen is purplish. The lines of growth are very remarkable, being few and 
