FRESH WATER AM) LAND SHELLS. 257 



rather long and thin; epidermis greenish, clouded with brown, slightly polished, with 

 rather minute, indistinct raysj 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. Tuomcy, were four of this species. One is an adult, the other 

 three arc young. It has somewhat the outline of U. rectus, Lam., and has on the exterior 

 a resemblance to l\ 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 decoratus. PI. XIII. Fig. G. 



Testa oblonza, valdi cojnpressd, in.vquilaterali ; valvulis sitblenuibus ; natibus prominulis, comprestis, ad 

 apices undulatis : epiJt rmide luteo-viridi, densisaime radial i; dentibut cardinalibus parvis, lamellatis; 



lati ralibus parvis rectisqite; margaritd alba et iridiscente. 



Shell oblon?, 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. 



Ilab. Abbeville District, S. C. Dr. Barratt and Mr. Tuomcy. 



My cabinet and cabinets of Dr. Barratt and Mr. Tuomcy. 

 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. III., Trans. 

 Am. Phil. Soc, PL XII. Fig. 22, under the name of Symp/iyiiolu {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- 

 milation 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 

 Btriffl arc close. The marks of growth distant. This species, like U. pressus, has the 

 Bymphynote character of the wing. 



