:i WATER AND LAND SHELLS. 2G7 



of the cardinal tooth; palleal cicatrices impressed; cavity of the slu 11 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 C irroratus, (Nobis,) was the first 

 described, and may be considered the type. There are now four known, all of which, \\ hile 

 casilv distinguished, have very much the same general characteristics, — irroratus, dramas, 

 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 dramas, 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 sccuris, (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 

 an' very different from caperatus. In the latter they are very close. In outline, the 

 Lamarckianus is nearly the same with intermedins, 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 vcrrucose character of it. It differs 

 also in the rays, which in intermedins arc arrow-head shaped. Indeed the intermedins 

 belongs to another group, of which mclanever, Raf., may be considered the type. 



I dedicate this beautiful species to the memory of the great naturalist Lamarck. 



Uniohebes. PI. XVIII. Fig. 21. 



'/', it&Isevi, oblongd, svbcompressd, ad latere planulatd, insequilaterali, poslice truncal it: valvulis snberassis} 

 natibw stibprominentibus, ml apices undulatis; epidermidt striata tenebroso-fuscd, eradiald ; dentibus cardi- 

 nalibus subcrassis, compressis, obliquis, acuminatis; lateralibus Imfsis curvisque; margaritd ullm. 



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, ray less; cardinal teeth 

 rather thick, compressed, oblique, acuminate : lateral teeth long and curved ; nacre white. 



I lab. Oconee river, near Athens, Georgia. Major Lc Conte. 

 .My cabinet and cabinet of Major Lc 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 

 Bmooth 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, 

 Cn nulate 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. 



