436 UNIONID^l. THEIR SOFT PARTS 



Remarks. — Tt is greatly to be regretted that we had not in these specimens a female 

 with the embryonic shell, as I believe it more than probable the form would be 

 wedge-shape, analogous to that of its allied species alatus. 



Unio purpuratus, Lam. An. sans Vert., vol. vi. p. 71. 



Branchial uterus occupies the posterior half of the outer branchiae, rounded and 

 enlarged at the end, in very large ovisacks, about twelve on each side. Branchiae 

 large, rounded below, inner ones rather the larger, united the whole length of the 

 abdominal sack. Palpi large oblique, united one-third down the posterior edges. 

 Mantle thin, thicker on the margin, which is broad. Branchial opening rather small, 

 with numerous, small, brownish papillae, inside of which there is a line of salmon 

 color and below this a dark brown line. Anal, opening small, with minute, scarcely 

 observable crenulations. The rim of the anus crenulate and the lower end pointed. 

 Super-anal opening rather large, colored on the edges and united below for a short 

 distance. Color of the mass whitish. 



Embryonic shell wedge-shape, light brown, has four well developed hooks, very like 

 alatus. See Jour. Acad. Nat. Sci. (2), vol. iv. pi. 5, fig. 25, and Obs. vol. vi. p. 48. 



Columbus, Mississippi, Dr. Spillman ; and Coosa River, Alabama, Dr. Showalter. 



Unio Claibornensis, Lea. Trans. Amer. Phil. Soc, (2), vol. vi. pi. 24, fig. 15, and Obs. vol. ii. p. 105. 



Branchial uterus occupies nearly the half of the posterior part of the outer branchiae 

 very like cariosus, the ovisacks being long and extending beyond the inferior line of 

 the leaf for one-tenth of an inch, blackish on the lower edges. Branchiae large, inner 

 ones rather the larger, united the whole length of the abdominal sack. Palpi large, 

 subelliptical, oblique, united half way down the posterior edges. Mantle thin, with 

 a broad border, much thickened below the branchial opening where there is a black 

 or deep brown line on a white fleshy expansion and fringed for some distance. 

 Branchial opening rather large, with numerous, brown papillae, and with a small 

 blackish round spot on each side below exteriorly. Anal opening small, with small, 

 brown papillae. Super-anal opening small, slightly colored within the edges and 

 united below. Color of the mass whitish. 



Embryonic shell elongate pouch-shaped, nearly clear white, has no hooks. 

 : Columbus, Mississippi, Dr. Spillman. 



Eemarlcs. — In one of the specimens I observed holes at the lower end of the ovi- 

 sacks, evidently made by the passing out of the embryonic shell. This is one of the 

 species which have the black spot on the mantle below the branchial opening. 



Unio trapezoides, Lea. Trans. Amer. Phil. Soc., (2), vol. iv. pi. 3, fig. 1. Obs. vol. i. p. 79. 



Branchial uterus . No ova were found here, but they were abundant in the 



