424 UNIONIDiE, THEIR SOFT PARTS 



Unto spatula-tub, Lea. Trans. Amer. Phil. Soc, (2,) vol. x. pi. 8, fig. 22 and Obs. vol. iv. p. 54 



Branchial uterus occupies the posterior half of the outer branchiae, colored on the 

 lower edges, with about fifteen large ovisacks in each of the outer leaves. Branchial 

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

 abdominal sack. Palpi small, subtriangular, united only a small distance down the 

 posterior edges. Mantle very thin, slightly thickened and colored on the edges. 

 Branchial opening rather large, with numerous small colored papillae. Anal open- 

 ing rather small, with very minute papillae. Super-anal opening somewhat large, 

 colored along the inner edges and united below. Color of the mass dirty white. 



Embryonic shell pouch shape, clear white, has no hooks. See Jour, Acad. Nat. Sci., 

 vol. iv. pi. 5, fig. 9. Obs. vol. vi. p. 47. 

 Fox River, Illinois, H. C. Grosvenor. 



Unio ligamentinus, Lam. An. sans Vert. vol. vi. p. 72. 



Branchial uterus occupies two-thirds the width of the outer branchiae and is enor- 

 mously distended, measuring two and half inches wide and one and a quarter long by 

 one-tenth thick. There were nearly forty ovisacks in each lobe, which was nearly 

 semicircular. These ovisacks extended nearly half an inch below the lower margin 

 of the branchiae. Branchial very large, nearly circular below, inner ones much the 

 larger, united the whole length of the abdominal sack. Palpi small, subelliptical, 

 united about one-third down the posterior edges. Mantle rather thin, thickened at the 

 margin and slightly colored at the edges. Branchial opening large, with numerous 

 small brownish papillae. Anal opening large, with an irregular creniform edge. 

 Super-anal opening large, colored within and united below. Color of the mass dirty 

 white. 



Embryonic s7iell pouch shape, clear white, has no hooks. See Journ. Acad. Nat. 

 Sci., (2) vol. iv. pi. 5, fig. 18 and Obs. vol. vi. p. 47. 



Fox River, Illinois, H. C. Grosvenor, and Columbus, Ohio, H. Moores. 



Remarlcs. — The ovisacks in the full grown of this species are of great size. In one 

 of the specimens measuring six inches wide, I found the uterus enormously extended, 

 and some of the ovisacks were one and a half inch long, four-tenths thick and two- 

 tenths wide. There were forty ovisacks on each side and a single one probably con- 

 taining over 10,000 embryonic shells, producing nearly a million in one season by a 

 single female ! This species seems to be another which has not papilla? on the annal 

 opening. 



Unio ebenus, Lea. Trans. Amer. Phil. Soc, (2) vol. iv. pi. 9, fig. 14. Obs. vol. vi. p. 94. 



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



Branchiae large, rounded below, inner ones much the larger, free nearly three-fourths 

 of the length of the abdominal sack. Palpi large, subelliptical, transverse, united 



