The 12th No. is in press and will contain the following new species:— 

 Unio cuneus. 



Shell obliquely cuneiform, very thick; diameter through the umbones 

 remarkably large; within pink. Resembles U. obliquus. Inhabits 

 Little Red river, Arkansas. 



Unio metastriatus. 

 A small species resembling U. interruptus, Raf., from the Black 

 Warrior river, Alabama; it has slightly raised radiating lines on the 

 posterior slope; whence its name. 



Unio lenis. 

 Obovate, regularly convex; epidermis brown olive, rayed. Inhabits 

 rivers in North Illinois. Distinguished from cariosus by its-dark epi- 

 dermis, rays over the whole disk, &c. 



Unio planilateris. 

 Oblong subovate, disks flattened; posterior slope with raised lines; 

 Inhabits Black Water, Yadkin and Neuse rivers. Allied to U. con- 

 garcBus. 



Unio iridescent. 

 Elliptical, compressed, thin; epidermis yellow, with rays on the 

 posterior side. Inhabits rivers in North Illinois. Resembles U.fascio- 

 laris in outline. 



Unio Scuveus. 

 Obovate, ventricose, thin, epidermis dark, yellowish-brown, rather 

 obscurely rayed. Inhabits Alabama river at Claiborne. Length 2 

 inches. 



Correginda. 

 Page 94, first fine from top, for "'was sent" read were sent. 

 " 91, for U. lienostts var. constrictu's, read U. constrictus. 

 38, pi. 18, fig. 1, is U.jisherianus, Lea. 

 45, for U. declivis, read U. sayanus, Ward. 



Note. — In the Trans. Philos. Soc, Pleiodon macmurtrii, nob. is 

 referred by Mr Lea to the Iridina ovata, Swain, because Mr. Gray 

 thinks them identical. This must be a wilful error on the part of Mr. 

 Lea. 



