J4 NEW UMONID.H OF THE 



smaller and thinner shell, more compressed and has not the well defined rays. It is 

 allied to nigellus (nobis) and torimis (nobis), but is not emarginate at the base like 

 the latter, nor has it the swollen umbonial slope nor the black polished epidermis of 

 it. It has a more regular biangular posterior margin than either. In the general 

 character of the soft parts there is a close alliance to nigellus. The posterior ends of 

 the branchi£B do not reach the margin, but are attached to it by a filamentous process. 

 The ova transferred to the branchial uterus were not matured, and therefore the 

 embryonic form could not be ascertained. 



Unio subniger. pi. 22, fig. 79. 



Testa Ixvi, elliptica, subcompressa, inequilatcrali, postice obtus6 angulata; valvulis subcrassis; natibus 

 prominulis; epidcrmide- tenebi-oso-fusca, nigricanto, striata, eradiatfi; dentibus cardiualibus parvius- 

 culis, erectis, aeuminatis cvcnulatisque ; lateralibus praelongis, lamellatis curvisquo; margarita alba et 

 iridescente. 



Shell smooth, elliptical, rather compressed, inequilateral, obtusely angular behind ; 

 valves rather thick ; beaks a little prominent; epidermis dark brown, nearly black, 

 striate, without rays; cardinal teeth rather small, erect, pointed and crenulate ; lateral 

 teeth very long, lamellar and curved ; nacre white and iridescent. 

 Proc. Acad. Nat. Sci., 1857, p. 172. 



Hah. — Flint Kiver, near Macon, Georgia. J. C. Plant. 



My cabinet and cabinet of Mr. Plant. 

 Diam. 1-1, Length 2, Breadth 3-G inches. 



Shell smooth, elliptical, rather compressed, inequilateral, obtusely angular behind, 

 obliquely rounded before, nearly straight on the basal line, substance of the shell 

 rather thick ; beaks a little prominent ; ligament long, thick and dark brown ; epi- 

 dermis dark brown, nearly black, transverely very much striate, without rays ; um- 

 bonial slope raised and slightly angular; cardinal teeth rather small, compressed, 

 erect, pointed and very much crenulate ; lateral teeth very long, lamellar and curved ; 

 anterior cicatrices large, distinct and well impressed ; posterior cicatrices large and 

 confluent ; dorsal cicatrices placed a little above the centre of the cavity of the beaks ; 

 cavity of the shell rather shallow and wide ; cavity of the beaks shallow and rounded ; 

 nacre white and iridescent. 



Soft Parts. — Branchial uterus occupies the whole width of the outer leaf of the 

 Branchia. Branchiw rather small, the inner one much the larger, very slightly 

 curved below, free nearly the whole length of the abdominal sack. Palpi rather 

 small, very transverse, subtriangular, united nearly half way down the posterior edges. 

 Mantle rather thick, thickened on the border. Branchial opening rather small, with 

 small brownish papilla; on the inner edges. Anal opening very small, with numerous 

 small brownish papilla?. Swper-nnal opejiing very large, the edges uncolored, united 

 below. Color of the mass dirtv white. 



