UNITED STATES AND NuKTlIEKN MEXKu X ri^**^' _/ ;-,i 



Institution. The dosoription, therefore, cannot he said to be perfect. The beak is too 

 much eroded to display any unduhitions which probably existed there. It reminds 

 one of a young, inflated ligamentiniis, Lam., also of irnmtti-i (nobis) and zicj-zag (nobis). 

 In outline it is very nearly the same as the two first, but is not quite so wide in the 

 axis major. In outline it is more elliptical than zig-zag, and the rays are different, 

 being more like venusfus and Ugamentlnus. This is another of the new molluscs 

 which the Smithsonian owes to the liberality of Lieut. Couch of the U. S. Army. 



Unio Berl.\ndiekii. pi. fif), fig. 194. 



Testa laevi, subquadrat;!, inflatii, postice subrotunda, insoquilaterali ; valvulis crassis, anticiS crassioribus ; 

 natibus grandibus, elcvatis, tumidis, ad apices minute undulatis; epidermide micante, tencbroso-fusca. 

 obsolete radiata; dentibus cardinalibus magnis, erectis, subcompressis, valdi crenulatiset in utroque val- 

 vulo duplicibus ; lateralibus longis, crassis, subcurvis lamcllatisque ; margarita vel purpurascentc vel 

 salmonis colore tincta et iridescente. 



Shell smooth, subquadrate, inflated, rounded behind, inequilateral ; valves thick, 

 thicker before ; beaks large, elevated, minutely undulate at the tips, .swollen ; epider- 

 mis shining, dark brown, ob.scurely radiated ; cardinal teeth large, erect, subcom- 

 pressed, very crenulate and double in both valves ; lateral teeth long, thick, some- 

 what curved and lamellar; nacre either purple or tinted with salmon color and 

 iridescent. 



Proc. Acad. Nat. Sci., 1857, p. 101. 



Hah. — Matamoras and Tamaulipas, Mexico. Lewis Berlandier, M. D. ; Colorado 

 River, Texas, Prof. Forshey. 



My cabinet and cabinets of Smithsonian Institution and Prof Forshey. 

 Diam. 1-7, Length 2-5, Breadth 3-4 inch. 



Shell smooth, subquadrate, inflated, rounded behind, inequilateral ; substance of 

 the shell thick, thicker before ; beaks large, raised, minutely undulate at the tips and 

 swollen ; ligament rather short, thick and dark brown ; epidermis shining, dark 

 brown, obscurely radiated, with distant brown bands of growth ; umbonial slope 

 rounded and inflated ; posterior slope wide, rather depressed, with three greenish 

 lines on each valve from the beaks to the margin ; cardinal teeth large, erect, rather 

 compressed, very crenulate and double in both valves ; lateral teeth long, thick, 

 somewhat curved and lamellar ; anterior cicatrices distinct, large, and well impressed ; 

 posterior cicatrices confluent, very large and slightly impressed; dorsal cicatrices 

 well impressed and placed across the cardinal tooth and on the under side of the 

 plate; cavity of the shell very deep and rounded ; cavity of the beaks very deep and 

 obtusely angular ; nacre either purple or tinted with salmon color and iridescent. 



Soft Rirts.— Branchial uferm filled through the whole length of the outer branchiae. 

 Branchio' rather large, quite semicircular, inner ones somewhat the larger, free at the 



14 



