450 UNIONIDiE, THEIR SOFT PARTS 



these papillae, and were quite sensitive to light. Anal opening small, without papillce, 

 the inner edge being variegated with lighter and darker brown. Super-anal opening 

 small, united for some distance below. Color of the mass salmon. 



Embryonic shell subtriangular, light brown, furnished with hooks which have 

 barbed points. See Jour. Acad. Nat. Sci. (2), vol. iv. pi. 5, fig. 36. Obs. vol. vi. p. 50. 



Othcalooga Creek, Georgia, Bishop Elliott, and Ohio River, D. H. Shaffer. 



Anodonta undulata, Say. Nicholson's Ency., Amer. Ed., pi. 3, fig. 6. 



Branchial uterus occupies the whole of the outer branchiae in transverse ovi- 

 sacks, and the whole presents a brownish appearance. See description and figure 

 in Trans. Am. Phil. Soc. (2), vol. vi. pi. 15, and Obs. vol. i. p. 52. Branchiae rather large, 

 curved below, inner ones the larger, united the whole length of the abdominal sack. 

 Palpi small, subtriangular, united nearly half way down the posterior edges. Mantle 

 rather thin, very much thickened at the margin, which is dark salmon at the base 

 and black posteriorly. Branchial opening rather large, with brown papilla?. Anal 

 opening rather large, with a few imperfect papilla? on the inner edges.* Super-anal 

 opening moderately large, united below. Color of the mass salmon, more intense on 

 the margin of the mantle and on the foot. 



Embryonic shell brown, triangular, has hooks. See Jour. Acad. Nat. Sci. (2), vol. iv. 

 pi. 5, fig. 38, and Obs. vol. vi. p. 50. 



Schuylkill, near Philadelphia, and Schuyler's Lake, New York, J. Lewis, M. D. 



Remarlcs. — The very remarkable arrangement and position of the ovisacks in this 

 species had my attention nearly thirty years since, and I described and figured them 

 in the 6th vol. 2d ser. of the Trans. Am. Phil. Soc, and in Obs. vol. vi. p. 52. A 

 more particular description and more correct figures were lately given in the Journal 

 Acad. Nat. Sci. (2), vol. iv. pi. 5, and Obs. vol. vi. p. 50. These embraced microscopic 

 views of the embryonic shell. More recently, having some living females, I closely 

 observed them for the purpose of discovering the mode of parturition. This is 

 effected by the extrusion of the whole sack, which is cylindrical with rounded ends, 

 and in the specimen observed, about one and a half inch wide, these ovisacks varied 

 in length from one-thirtieth to one-fourth of an inch long, containing from one to ten 

 ova. The ovisack is extruded with the embryo still in the ovum, but they soon 

 begin to appear at the surface of the ovisack, and are there fastened apparently by a 

 filament at the dorsal line. Desirous of knowing with what rapidity these ovisacks 

 were extruded by the parent, I observed closely the daily number. On the 14th of 

 January, 1855, I observed five ovisacks in the water; on the morning of the 15th I 



* Agassiz's genus Strophitus, (Stimpson's Shells of New England, p. 15), of which undulata is the type, is 

 stated not to be fringed at the anal opening, but I find it to be partially fringed. TJnio radiatus is usually 

 fringed, but in some cases is not so. 



