NEW UNIONISE OF THE UNITED STATES. 107 



green lines from the beaks to the posterior margin ; cardinal teeth small, compressed, 

 single in both valves and not crenulate ; anterior cicatrices confluent, very slightly 

 impressed; posterior cicatrices continent and very slightly impressed; dorsal cicatrices 

 placed on the inner and upper side of the cavity of the beaks ; cavity of the shell 

 rather deep and rounded ; cavity of the beaks rather shallow and subangular ; nacre 

 thin, bluish white, salmon color towards the beaks and iridescent. 



Soft parts. — Branchial uterus not charged. In three mature specimens in alco- 

 hol, I could find no ova in the ovarium, but there seemed to be well formed 

 ovisacks. BrancJiice very large, rather thick, rounded below, inner ones much the 

 larger, united nearly half the length of abdominal sack. Palpi rather wide, suboval, 

 thin, united half way down the posterior edges. Mantle thin, with a broad margin,- 

 thickened at the edges, with blackish spots along the posterior margin on the exterior 

 edges. Branchial, opening rather large, with numerous, rather small, reddish brown 

 papillce. Anal opening rather small, reddish and maculate within, with numerous 

 very small, reddish brown papillae on the inner edges. Anus regularly crenulate. 

 Super-anal opening small, united for some distance below and maculate on the outside. 

 Color of the mass whitish. 



BemarJes. — I have seven specimens from Dr. Spillman — all adult. The one figured 

 is the smallest and most perfect. In outline and general appearance, this species 

 resembles Anodonta unclulata. Say, and Anodonta edentula (nobis), — Alasmodonta 

 edentula, Say, but it is more regularly elliptical than either of them, and there is a 

 well-defined subtuberculous tooth in both valves, which is never found in both valves 

 of the other two, and which really separates them generically from this shell. It is 

 closely allied to Margaritana Elliottii (nobis), but is larger and not so cylindrical. The 

 undulations on the beaks are also more concentric. The fine yellow, wavy rays are 

 well marked in some specimens, as they pass through the green epidermis. The yel- 

 low color prevails on the anterior and posterior slopes. It is to be regretted that 

 neither of the specimens, in alcohol, had charged branchial uteri that the character 

 of that important organ might be detected and described. 



Margaritana Tombigbeensis. PI. 18, fig. 255. 



Testa leevi, elliptic;!, inflata, postice obtuse angulatil, atitice rotundata, subrequilaterali ; valvulis subtenui- 

 bus ; natibus promiDentibus, tumidis, ad apices rugoso-undulatis; epidermide vel teuebroso-oliva vel 

 nigricente, obsolete radiata; dentibus cardinalibus parvis, compresso-tuberculatis; margarita alba et 

 iridescente. 



Shell smooth, elliptical, inflated, obtusely angular behind, rounded before, sub- 

 equilateral ; valves rather thin ; beaks a little prominent, swollen, rugosely undulate 

 at the tips; epidermis dark olive, sometimes nearly black, obscurely rayed; cardinal 

 teeth small, compressed, tuberculate ; nacre white and iridescent. 

 Proc. Acad. Nat. Sci. 1858, p. 138 



