137 
fore^ agreeably to any rules of modern nomenclature^ the name 
purpureus seems fated to withstand all attacks, unless, indeed, it 
can be proved, from Mr. Dillwyn’s description itself, that he meant 
this shell, when he described his complanatuSj and not that of the 
figure to which he refers. 
Alasmodonta sculptilis. — Shell transversely suboval, with 
green radiations : umbo and summit with six or seven rather sharp 
undulations, which are transverse, rectilinear, at the extremities 
abruptly arquated or reflected : dorsal and anterior margin from 
the summits with numerous, slender, slightly elevated lines bend- 
ing in diflerent directions. 
This is evidently a young shell, but we know nothing of the 
adult. The teeth are more like those of the undulata, nob., than 
any other species, but the form and sculptured anterior margin 
amply distinguish it. 
It was brought from Virginia by Mr. I. Lukens, and by him 
presented to me. 
Alasmodonta edentula. — Shell transversely oblong-oval, 
somewhat compressed, dark olivaceous or brownish, obsoletely 
radiated (in the young :) nates behind the middle, but remote from 
the posterior edge, but little prominent, undulated : anterior mar- 
gin not remarkably compressed, and not radiated: within white, 
margined with opake white more or less distinct, but sometimes 
obsolete : teeth obsolete, but the peculiar curvature beneath the 
beaks shows their locality. 
Length, one inch and seven-tenths ) breadth, three inches. Con- 
vexity, one inch. Inhabits Wabash river. 
Approaches nearest to A. marginata, nob. ; but the want of 
teeth, and the simple anterior margin, at once distinguish it. 
Ctclas edentula. — Shell transversely oval, inequilateral, 
with somewhat elevated and regular transverse lines : beak not ele- 
vated above the general surface ; cardinal tooth very small, lineolar, 
oblique and not elevated higher than the edge of the hinge mar- 
gin : color brown : umbones decorticated. 
Length, seven-twentieths of an inch. Breadth, two-fifths of an 
inch. Inhabits Canandaigua Lake. 
This is distinguishable by the diminutive teeth, which are not 
visible in a profile view of the hinge. 
12 
