100 NEW UNIONID.?; OF THE UNITED STATES. 



Shell sulcate, subtriangular, very much inflated, flattened at the sides, nearly equi- 

 lateral ; valves somewhat thick, thicker before ; beaks somewhat prominent, slightly 

 inflated ; epidermis dark reddish brown, without rays, shining above and striate be- 

 low ; cardinal teeth rather thick, raised, subpyramidal and crenulate; lateral teeth 

 rather long, curved and somewhat thick ; nacre rose-colored, white or salmon and iri- 

 descent. 



Proc. Acad. Nat. Sci. 1861, p. 40. 



Hah. — Tombigbee River, Mississippi. W. Spillman, M. D. ; Coosa River and Big 

 Prairie Creek, Alabama. E. R. Showalter, M D. 



My cabinet and cabinets of Dr. Spillman, Dr. Showalter and Dr. Hartraan. 

 Diam. 1-1, Length 1-7, Breadth 2-2 inches. 



Shell sulcate, subtriangular, very much inflated, flattened at the sides, subequi- 

 lateral; substance of the shell rather thick, thicker before; beaks somewhat promi- 

 nent and slightly inflated ; ligament rather large and dark brown ; epidermis dark 

 reddish brown, without rays, shining above and striate below, with numerous, rather 

 close lines of growth ; umbonial sloi^e raised into a well-defined angle ; posterior slope 

 broad, very dark brown, with two impressed lines from the beaks to the margin in 

 each valve ; cardinal teeth rather thick, elevated, somewhat pyramidal and crenulate ; 

 lateral teeth rather long, curved and somewhat thick ; anterior cicatrices distinct, 

 rather large and deeply impressed ; posterior cicatrices confluent, lai'ge and well im- 

 pressed ; dorsal cicatrices placed on the under side of the plate within the cavity of 

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

 angular; nacre rosaceous, white or salmon tinted and iridescent. 



Soft parts. — Branchial iiterus not charged. Ova were found in the ovarium only. 

 BrancMce very lai'ge, curved below, inner ones much the lai'ger, free two-thirds the 

 length of abdominal sack. Palpi large, subtriangular, united half way down the pos- 

 terior edges. Mantle very thin, with a very broad border. Branchial opening large, 

 with numerous small papillog on the inner edges. Anal opening large, with very 

 minute, closely-set papillas on the inner edges. Super-anal opening very large, edges 

 colored, united below ; color of the mass whitish. 



Remarlcs. — The soft parts of these specimens were not in good order, and were 

 blackened by the liq-aor or some other matter. There was no appearance of redness 

 in the ova as in the kindred species ruhiginosm. This species is, in many characters, 

 closely allied to riibiginosus, but it differs in being much more inflated, in being sulcate, 

 in being more quadrate, and in having the lines of growth much more close. Two 

 specimens of ruhiginosus were received from Dr. Spillman, with several rubiclus. An 

 adult of the former has but three marks of growth. In all of the adults of the latter 

 there are seven or eight such marks. In all the specimens before me the epidermis 



