434 UNIONISE, THEIR SOFT TARTS 



broad thin margin, colored at the edges. Branchial opening very large, with nume- 

 rous minute papillae slightly colored. Anal opening rather large, without papillae 

 but slightly crenulated. Super-anal opening very large, colored on the edges and 

 slightly united below. Color of the mass whitish, the superior part being raised very 

 much into the arch of the cavity. 



Cincinnati, Ohio, T. G. Lea and J. Clark. White River, Indiana, D. H. Shaffer. 



Remarks . — Among ten specimens, in alcohol, from Mr. Clark, none had ova. They 

 appeared all to be males, but some specimens sent to me in 1827 by my brother, 

 T. G. Lea, in alcohol, and in a dried state also, enabled me then to describe the very 

 extraordinary arrangmentof the branchial uterus. See Trans. Amer. Phil. Soc. (2), 

 vol. iii. pi. 5, fig. 5, and Obs. vol. i. p. 11, where I have fully described this singular 

 arrangement. It is, as far as my observation has extended^ the only species which 

 has even an approach to the extraordinary arrangement of the ovisacks. I have 

 described, as referred to above, their curious geometrical adaptation to the small 

 cavity or area of the interior. It is greatly to be regretted that the embryonic shell 

 has not yet been observed, as it might present some novelty co-ordinate with the 

 unique ovisacks. I have in vain endeavored to obtain the female with mature 

 embryonic shells. Of two specimens, both males, from White River, sent to me in 

 a living state, one had a blackish exterior border to the mantle, while the other was 

 maculate, as the Margaritana usually are. 



Unio gracilis, Bar. Am. Jour. Sci., vol. vi. p. 274. 



Branchial uterus occupies the posterior fourth part of the outer branchiae, being 

 rounded below and having three rows of crenulations. No ova were found here, but very 

 minute ones were in the ovarium. Branchiae rather large, thick, much rounded below, 

 the inner ones very oblique posteriorly and rather the larger, united the whole length 

 of the abdominal sack. Palpi very large, thick, suboval, obtusely angular at the end, 

 united for a short distance down the posterior edges. Mantle rather thin, with a 

 broad margin, thickened, doubled and blackish on the posterior edges. Branchial 

 opening rather small, crowded with numerous brownish papillae. Anal opening small, 

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

 edges and united for a short distance below. Color of the mass dirty white. The 

 adductor and tractor muscles are very large. 



Cincinnati, Ohio, J. Clark. Columbus, Mississippi, Dr. Spillman. 

 Remarks. — It is greatly to be regretted that none of the specimens received had 

 the embryonic shell, as we might expect in this winged species to find the wedge- 

 shape form, as in Iwvissimus and alatus, all three being much raised in the wing and 

 connate over the ligament. Those from Columbus were sent in November, and the 

 ova were found in the ovarium, so minute as to require a high power to detect them. 



