AND EMBRYONIC FORMS. 443 



BemarJcs. — The specimens being dried, the description is consequently imper- 

 fect. They were taken September 28, 1838. The shell which I described under 

 the name of sulcatus is the male of ridibundus, and is usually much larger than the 

 female. 



Unio poliatus, Hild. Am. Journ. Sci., vol. 14. 



Branchial uterus occupies the whole width of the outer branchiae, very much like 

 ridibundus. Branchial rather small. Mantle thickened on the margin, with elongate 

 ciliae on the inner edge and an extended flap below the branchial opening. 



Embryonic shell subtriangular, white, has no hooks, nearly the same as undulatus, 

 Hild. See Journ. Acad. Nat. Sci., (2,) vol. iv. pi. 5, fig. 22. Obs. vol. vi. p. 48. 



Cincinnati, Ohio, T. G. Lea. September 28, 1838. 



Remarks. — An imperfect dried specimen and, of course, an imperfect description. 



Unio subgibbosus, Lea. Jour. Acad. Nat. Sci., (2,) vol. iv. pi. 6, fig. 36. Obs. vol. vi. p. 53. 



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



Branchice very wide, very thin, and curved below, inner ones much the larger, free 

 nearly the whole length of the abdominal sack. Palpi very small, thin, oblique, sub- 

 oval, united only at the upper posterior edges. Mantle very thin, thickened at the 

 inferior edges, dirty white. Branchial opening large, with numerous small, brownish 

 papillae. Anal opening large, with very numerous small, blackish papillae. Super- 

 anal opening rather large, lined on the edges and united below. Color of the mass 

 dirty white. 



Coosa River, near Wetumpka, Alabama, E. R. Showalter, M. D. 



Unio fibuloides, Lea. Journ. Acad. Nat. Sci., (2,) vol. iv. pi. 28, fig. 100. Obs. vol. vii. p. 37. 



Branchial uterus . No ova were found here, but they were in the ovarium. Bra?i- 



chice small, semicircular, inner ones rather the larger, free nearly the whole length of 

 the abdominal sack, united to the edge by a filament. Palpi small, subovate, united 

 a short distance on the posterior edges. Mantle thin, thickened on the margin. 

 Branchial opening small, with very small, brownish papillae. Anal opening small, 

 with minute, brownish papillae on the inner edges. Super-anal opening small, slightly 

 united below. Color of the mass dirty white. 



Coosa River, near Wetumpka, Alabama, E. R. Showalter, M. D. 



Unio Formanianus, Lea. Trans. Ainer. Phil. Soc, (2,) vol. viii. pi. 27, fig. 64. Obs. vol. iii. p. 85. 



Branchial uterus occupies the lower half of the whole width of the outer bran- 

 chiae ; and lies in folds like phaseolus and Woodwardiaims. (See figures in Journ. 

 Acad. Nat. Sci., (2,) vol. iv. pi. 29 and Obs. vol. viii. pi. 29, figs. 101 and 103.) 

 Branchice large, thin, nearly semicircular, inner ones much the larger, free about half 



