FRESH WATER AND LAND SHELLS. 13 
rather long and thin; epidermis greenish, clouded with brown, slightly polished, with 
rather minute, indistinct rays; cardinal teeth large, pointed, single in the right and double 
in the left valve; lateral teeth long, somewhat curved and thickened at the posterior end; 
anterior cicatrices distinct; posterior cicatrices confluent; dorsal cicatrices placed in the 
centre of the cavity of the beaks; cavity of the shell shallow; cavity of the beaks small 
and rather angular; nacre white, purplish, or delicately salmon coloured and iridescent. 
Remarks.—Among many interesting species—several of which were new—received 
from Dr. Barratt and Mr. Tuomey, were four of this species. One is an adult, the other 
three are young. It has somewhat the outline of U. rectus, Lam., and has on the exterior 
a resemblance to U. nasutus, Say, but is a thicker shell. It is not so cylindrical as the 
rectus, nor so wide. It is allied to U. Tuomeyi, but is a wider species. 
Unio pecoratus. Pl. XII. Fig. 6. 
Testa oblonga, valdé compressa, inxquilaterali ; valvulis subtenuibus ; natibus prominulis, compressis, ad 
apices undulatis ; epidermide luteo-viridi, densissimé radiaté; dentibus cardinalibus parvis, lamellatis ; 
lateralibus parvis rectisque; margarita alba et iridiscente. 
Shell oblong, much compressed, inequilateral ; valves rather thin; beaks slightly prominent, compressed, undu- 
lated at the beaks; epidermis yellowish-green, closely radiated; cardinal teeth small, lamellar; lateral teeth small 
and straight; nacre white and iridescent. 
Hab. Abbeville District, S.C. Dr. Barratt and Mr. Tuomey. 
My cabinet and cabinets of Dr. Barratt and Mr. Tuomey. 
Diam. .8, Length 1.4, Breadth 2.3 inches. 
Shell oblong, much compressed; posterior dorsal margin carinate ; substance of the 
shell rather thin, slightly thickened before; beaks slightly prominent, compressed and 
crowded with double concentric undulations; ligament very small, thin, nearly concealed 
within the valves; epidermis yellowish-green, with numerous capillary rays over nearly 
the whole disk; cardinal teeth rather small, lamellar, single in the right and double in the 
left valve; lateral teeth rather short, straight and acicular; anterior cicatrices distinct; 
posterior cicatrices confluent; dorsal cicatrices situated in the point of the cavity of the 
beaks; cavity of the shell rather shallow; cavity of the beaks small and angular; nacre 
white, rather brilliant and iridescent. 
Remarks.—I owe to the kindness of Dr. Barratt and Mr. Tuomey four specimens of 
this interesting species, which draws more attention from the fact of its forming a natural 
link with a highly interesting species which I described and figured in Vol. IIL., Trans. 
Am. Phil. Soc., Pl. XII. Fig. 22, under the name of Symphynota (Unio) compressa, after- 
wards changed to pressus. It differs from the pressus, however, in being less oblong, in 
being rather more inflated and less lenticular. In the teeth, while there is a strong assi- 
mnilation to that peculiar character of the pressus, there is a marked difference; the eleva- 
tion of the posterior portion of the cardinal tooth being very much less, and the two bifid 
portions much closed. The umbonial slope is disposed to be angular. The transverse 
strie are close. The marks of growth distant. This species, like U. pressus, has the 
symphynote character of the wing. 
