402 UNIONIDJE, THEIR SOFT PARTS 



of the Acad. Nat. Sci., I have published descriptions of the soft parts of ninety-one 

 species, which, with those herein described, will make two hundred and thirty-four. 



Genus UNIO. 



Unio luteolus, Lam. An. sans. Vert., vol. vi. p, 79. 



Branchial uterus large. In the fine specimen under examination, there are about 

 forty large ovisacks on each outer branchia, each one of which ovisacks contains a 

 large number of embryos of a regular pouch shape.* These sacks occupy nearly 

 the half of the outer branchiae posteriorly. In this it resembles cariosus and ochra- 

 ceus. Branchial rather large, curved below and united the whole length of ab- 

 dominal sack. Palpi rather large, subtriangular and united one-fourth down the 

 posterior edges. Mantle rather thick, much thickened at the margin. Branchial 

 opening large, with numerous large brown papilla?, which continue below to the 

 basal margin. Below the branchial opening, on the outside, there is a black, round 

 spot on each side of the mantle, putting on the appearance of eyes. These are 

 more observable in the females than the males. Anal opening small, with numerous 

 small, light-brown papillae. Super-anal opening^ rather small, lined on the inner 

 edges and united below. Color of the mass whitish, the foot being light salmon 

 color. 



Remarks. — In the female there is a fleshy process like that in radiatus,% some 

 distance below the branchial opening, which is fringed, and the papillae extend be- 

 low the process. One of the females under examination was found to form the 

 super-anal opening into four distinct holes, — the three posterior ones round, the an- 

 terior one subovate. This species is very widely distributed, being found in the 

 Mississippi, Missouri and Ohio basins, as well in the St. Lawrence and Moose Rivers, 

 in the Great Lakes, Winnipeg and Slave Lakes and River Sascatchawan. 



Unio paulus, Lea. Trans. Amer. Phil. Soc, vol. viii. pi. 15, fig. 9 and Obs. vol. iii. p. 51. 



Branchial uterus small, placed on the posterior portion of the branchiae, with about 

 ten sacks like heterodon, the edges tipt with black. Branchial small, thin, the inner 

 ones much the larger, curved below, free nearly the whole length, of the abdominal 

 sack. Palpi small, subtriangular, not united on the posterior edges. Mantle very 

 thin, with a dark line on the outer posterior edges. Branchial opening rather large, 

 with numerous light-brown papillae on the inner edges. Anal opening rather small, 

 with numerous small papillae. Super-anal opening rather large and united below. 

 Color of the mass whitish to light salmon. 



* See Journal Acad. Nat. Sci., vol. iv. pi. 5, fig. 10 and Obs. vol. vi. p. 47. 

 t This is called by Pfeiffer the slit of Bojanus. 

 j Trans. Amer. Phil. Soc. vol. vi. pi. 15, fig. 49, 



