FRESH WATER AND LAND SHELLS. 23 
of the cardinal tooth; palleal cicatrices impressed; cavity of the shell very shallow; cavity 
of the beaks rather deep and angular; nacre silvery white. 
Remarks.—The curious and beautiful interrupted rays which cover the whole disk of 
this species, bring it into the group of which the U. wroratus, (Nobis,) was the first 
described, and may be considered the type. There are now four known, all of which, while 
easily distinguished, have very much the same general characteristics,—irroratus, dromas, 
caperatus and Lamarckianus. The five specimens before me are of different sizes. The 
largest is the most perfect one, and is that which is figured. It is about the size of a 
young dromas, when about to finish its two humps. It differs from all the other three 
species, in having an angular ridge from the beaks to the posterior basal margin. The 
beaks are remarkably compressed and pointed, like securis, (Nobis.) The nodules are 
little more than rugosities, disposed to run into small folds. Both this and caperatus 
might be said scarcely to belong to the nodulous division of the genus, but they are cer- 
tainly not devoid of nodules, though they are small and irregular. The lines of growth 
are very different from caperatus. In the latter they are very close. In outline, the 
Lamarckianus is nearly the same with intermedius, Con., from Tennessee. It cannot, 
however, be confounded with that species, as it has not the furrow which that shell has 
on the posterior slope; nor has it the well expressed verrucose character of it. It differs 
also in the rays, which in intermedius are arrow-head shaped. Indeed the intermedius 
belongs to another group, of which metanever, Raf., may be considered the type. 
I dedicate this beautiful species to the memory of the great naturalist Lamarck. 
Unio nezes. PI. XVIII. Fig. 21. 
Testa levi, oblonga, subcompressd, ad lateré planulata, inequilaterali, posticé truncata; valvulis subcrassis: 
natibus subprominentibus, ad apices undulatis ; epidermide striata tenebroso-fuscd, eradiata dentibus cardi- 
nalibus subcrassis, compressis, obliquis, acuminatis ; lateralibus longis curvisque; margarita alba. 
Shell smooth, oblong, rather compressed, flattened on the side, inequilateral, truncate behind; valves rather 
thick; beaks somewhat prominent, undulate at the tip; epidermis striate, dark-brown, rayless; cardinal teeth 
rather thick, compressed, oblique, acuminate ; lateral teeth long and curved; nacre white. 
. . . > 
Hab. Oconee river, near Athens, Georgia. Major Le Conte. 
My cabinet and cabinet of Major Le Conte. 
Diam. .8, Length 1.3, Breadth 2.2 inches. 
Shell smooth, oblong, rather compressed, flattened on the side, inequilateral, truncate 
behind, rounded before; substance of the shell rather thick, beaks somewhat prominent, 
undulated at the tip and submedial; ligament rather long, thin and nearly covered ; epider- 
mis dark brown, without rays, thickly striate over the lower half of the shell, thick and 
smooth above; lines of growth not well defined; posterior slope compressed into an 
elevated carina, with a slightly impressed furrow, which has two very obscure raised lines; 
umbonial slope rounded; cardinal teeth rather thick, compressed, oblique, acuminate, 
crenulate and double in both valves; lateral teeth long, curved and thickened at the pos- 
terior end; anterior cicatrices distinct; posterior cicatrices confluent; dorsal cicatrices 
placed nearly in the centre of the cavity of the beaks; cavity of the shell shallow and 
wide; cavity of the beaks shallow and obtusely angular; nacre white. 
