442 UNIONIDiE, THEIR SOFT PARTS 



Anal opening small, with numerous very small, dark-brown papillae. Super-mud 

 opening large, deeply colored on the edges and slightly united below. Color of the 

 mass whitish. 



Unio obscurus, Lea. Trans. Amer. Phil. Soc, (2,) vol. vi. pi. 3, fig. 7, and Obs. vol. ii. p. 7. 



Two specimens only received, both males. 



Branchiae large, nearly semicircular, light liver-brown, united the whole length of 

 the abdominal sack, the inner lobes have a thin whitish line along the lower edge. 

 Palpi rather small, thick, suboval, united half way down the posterior edges. 

 Mantle rather thin, thickened on the margin, dark-brown and with dark papillae 

 on the margin below the branchial opening. Branchial opening large, with numerous 

 long, thin, brown papillae. Anal opening small, with very minute, brownish papillae. 

 The border, inside, beyond the papillae, is larger than usual, and is dark striped on 

 a light-brown ground. Super-anal opening rather small, with dark spots on the 

 inner margin, united below. Color of the mass very light salmon, almost white. 



White Eiver, Indiana, D. H. Shaffer. 



Unio personatus, Say = (papillaris, Lea.) Disseminator, 1829. 



Branchial uterus occupies the whole width of the outer branchiae. 



Embryonic shell white, subrotund, without hooks, very nearly like perplexus. See 

 Journ. Acad. Nat. Sci., (2,) vol. iv. pi. 5, fig. 21, and Obs. vol. vi. p. 48. 



Remarks. — The above imperfect description was made from a dried specimen sent 

 by my brother twenty-five years since. It was taken September 28, 1838. The 

 young seem to occupy the whole width of the branchiae, but not the upper part. 



Unio heterodon, Lea. Trans. Amer. Phil. Soc., (2 r ) vol. iii. pi. 8, fig. 11, and Obs. vol. i. p. 42. 



Branchial uterus occupies the whole width of the outer branchiae. 



Embryonic shell subtriangular, white, has hooks, and is closely allied to pressus 

 in form. See Journ. Acad. Nat. Sci., (2,) vol. iv. pi. 5, fig. 23. Obs. vol. vi. p. 48. 



Remarks. — The above imperfect description was made from a dried specimen 

 taken March 20th in the Schuylkill, near the Palls. 



Unio ridibundus, Say (= sulcatus, Lea.) Am. Conch., pi. 5. 



Branchial uterus occupies nearly the whole length of the outer branchiae, very 

 like to heterodon. Branchial opening is blackish, and has small, very dark papillae. 

 The mantle is enlarged below the branchial opening, is very black on the posterior 

 margin and has a few papillae. 



Embryonic shell pouch-shape, white, has no hooks, very nearly the same with 

 phaseolm, Hild. See Journ. Acad. Nat. Sci., (2,) vol. iv. pi. 5, fig. 12, and Obs. vol. 

 vi. p. 47. 



Cincinnati, Ohio, T. G. Lea. 



