35 



SYNONYMES. 



U. crassus, Say. Nich. Enc. (Amer. ed.) art. Conch, pi. i. tig. 



8. old male. 

 U. crassidens, var. c. Lam. An. sans vert. vol. vi. p. 71. 



U. LIGAMENTINA, ib. p. 72. 



U. ellipticus, Barnes. Silliman's Jour. vol. vi. p. 259. male. 

 U. suborbiculatus, Hildreth. Silliman's Jour. vol. xiv. female. 

 U. abruptus, Say. Amer. Conch, pi. 17, female, var. A. male. 

 U. cyclops, Eaf. Contin. of Monog. p. 2, female. 

 Cab. A. N. S. No. 358. 



OBSERVATIONS. 



Closely related to U.fascialus, Raf., but can be dis- 

 tinguished from that species by fewer and narrower 

 rays, generally distinct only over the umbones; by a 

 lighter coloured more polished epidermis; more pro- 

 minent teeth, and the prevalence of a salmon co- 

 loured interior. Common in the rivers of Ohio, 

 Indiana, and Illinois, but appears to be rare in the 

 more southern states. I could not find it in the 

 rivers of Alabama. The specimen figured was pre- 

 sented by Dr. Blanding. 



UNIO VIRIDIS. 



Plate XVII.— Fig. 1. 



DESCRIPTION. 



Shell elliptical or subovate, ventricose, thin; disks 

 slightly flattened anteriorly, much inflated over the 

 umbonial slope; lines of growth prominent; ligament 

 margin elevated; posterior slope dilated; posterior 



