52 NEW UNIONID.*: OF THE 



rathei' small and placed above the centre of the cavity of the beaks ; cavity of tlie 

 shell small ; cavity of the beaks small and subangular ; nacre bluish white and very 

 iridescent. 



Soft Parts. — BrancMal uterus filled the whole length of the outer branchias except 

 at the posterior end * Brancliice rather large, very transverse, gently curved below, 

 the inner ones much the larger, free half the length of abdominal sack. Palpi small, 

 subtriangular, angular at the point, united only at the upper part of posterior edges. 

 Mantle thin, thicker at the margin and slightly colored at the edges. Branchial 

 opening rather large, with numerous small brownish papillje. Anal opening rather 

 large with numerous very small papillfe on the inner edges. Super-anal openmg 

 very long, blackened on the inner edges and slightly united below. Color of the 

 mass whitish. 



Remarhs. — This belongs to the complanatus group, and very closely resembles the 

 thin white varieties. It approaches the outline of Dariensis, (nobis.) and the epider- 

 mis is nearly of the same color. It is. however, a much smaller and a much thinner 

 shell. It is very graceful in form. It has four or five marks of growth which are 

 very distant. It is disposed to be shining on the umbones and striate towards the 

 margin. 



Unio subellipsis. pi. 10, fig. 44. 



Testa liBvi, elliptica, inflata, inaequilaterali, ad basim rotunda ; valvulis erassis ; natibus subprominentibus ; 

 epiderinide tenebroso-brunnea, polita radiataque ; dentibus cardinalibus brevibus, tumidis, subelevatis- 

 que ; lateralibus prselongis subrectisque ; margarita argentea et iridescente. 



Shell smooth, elliptical, inflated, inequilateral, rounded at the base ; valves thick ; 

 beaks somewhat prominent ; epidermis dark brown, polished, rayed ; cardinal teeth 

 short, thick, rather elevated ; lateral teeth very long and nearly straight ; nacre silver 

 white and iridescent. 



Proe. Acad. Nat. Sci. 1856, p. 262. 



Hah. — Creeks near Columbus, Georgia. Bishop Elliott. 



My cabinet and cabinet of Bishop Elliott. 

 Diam. 1, Length 15, Breadth 2-5, inches. 



Shell smooth, elliptical, inflated, inequilateral, rounded at the base, rather com- 

 pressed before and dilate behind ; substance of the shell thick, slightly thinner behind ; 

 beaks somewhat prominent ; ligament rather short and thin ; epidermis dark brown, 

 polished, obscurely rayed before, distinctly and broadly rayed behind ; cardinal teeth 

 small, short, thick, rather elevated and double in both valves ; lateral teeth very long 

 and nearly straight; anterior cicatrices distinct; posterior cicatrices confluent; dorsal 

 cicatrices placed on the plate in the centre of the cavity of the beaks : cavity of the 



*There was only a single female, and as this character of not being charged at the posterior end is nnusual, 

 it may be different in other individuals. 



