438 UNIONIDjE, THEIR SOFT PARTS 



length of the abdominal sack. Palpi rather large, very transverse, somewhat thick, 

 subelliptical, united nearly half way down the posterior edges. Mantle rather thick, 

 with a broad margin, crenulated on the edges below the branchial opening. Branchial 

 opening large, with very small, dark brown papillae. Anal opening small, without 

 papillae, but slightly crenulate on the inner edges. Super-anal opening rather large, 

 united below. Color of the mass dirty white. 



Columbus, Mississippi, Dr. Spillman. Rutersville, Texas, Prof. Forshey. 



Remarks. — The ova found in the branchial uterus were very small, perfectly round 

 and granulated in the middle. They were found also in the ovarium. This is an- 

 other species of Unio which has no papillae in the anal opening. 



Unto ctrculus, Lea. Trans. Anier. Phil. Soc, (2,) vol. iii. pi. 9, fig. 14, and Obs. vol. i. p. 47. 



Only three specimens were received, all being males. Branchke rather large, 

 somewhat thick, nearly semicircular, united the whole length of the abdominal sack. 

 Palpi rather small, subtriangular, united one-third down the posterior edges. Mantle 

 very thin, thickened on the margin, furnished with very minute papillae below the 

 branchial opening. Branchial opening rather small, with numerous small, brownish 

 papillae. Anal opening rather small, with very minute papillae. Super-anal opening 

 rather large, colored on the inner edges and united below- Color of the mass whitish. 



Columbus, Mississippi, Dr. Spillman. 



Unio crocatus, Lea. Trans. Am. Phil. Soc. (2) vol. viii. pi. 22, fig. 52. Obs. vol. iii. p. 76. 



Branchial uterus occupies, very much like ochraceus, more than half of the poste- 

 rior portion of the outer branchiae, one of the specimens having about forty ovisacks 

 on each side, the longest being seven-tenths of an inch long. The whole lobe is 

 nearly semicircular, and the lower portion is black, with a bright brown border. 

 None of the ova in any of the specimens were advanced beyond granulation, and yet 

 the ovisacks seemed ready to be extruded by the parent, enveloped together in the 

 integuments of the sack, as I have observed in U. complanatus. Branchial large, 

 nearly semicircular, inner ones much the larger, united the whole length of the 

 abdominal sack. Palpi rather large, subtriangular, united about one-third down 

 the posterior edges. Mantle rather thin, with a very broad margin, slightly colored 

 on the lower edges, much thickened below the branchial opening, where it is black 

 and reddish brown and furnished with papillae on the inner edges. Branchial opening 

 rather large, black and reddish brown, with numerous papillae. Anal opening rather 

 small, with numerous very small papillae. Super-anal opening large, colored on the 

 inside and united below. Color of the mass whitish. 



Columbus, Mississippi, Dr. Spillman. 



Remarks. — This species is closely allied to ochraceous, but the outer hard parts are 



