50 Trans. Acad. Sci. of St. Louis. 



Oyrena or to a Cyprina in color, and general character of the 

 epidermis, will serve to readily distinguish it from all related 

 forms. 



Unio SECURI8 Lea. 



Trans. Am. Philos. Soc.,Vol. Ill, 1829, p. 437, PI. XI, 

 Fig. 17 ; embryo figured in Jour. Acad. Nat. Sci. Phila., 

 2d series. Vol. IV, p. 47, PI. V, Fi^. 6, 1858; Reeve, 

 Conchologia Iconica, Vol. XVI, Unio Plate LXI, Fig. 

 304, 1868. Described from the Ohio. 



Unio ?zneo?a^wsRafinesque. So Say, in American Con- 



chology, Plate XLVIII. This part, VII, is undated and 



was published by Mr. T. A. Conrad, after Mr. Say's 



death. 



The only occurrence to us, in Arkansas, of this shell was in 



the St. Francis river, at Wittsburg, where it is commonly 



found on the muddy bottoms in great numbers and of large 



size. Its cuneiform shape separates it readily from all others 



likely to be found in Arkansas. 



Unio speciosus Lea. 



Jour. Acad. Nat. Sci. Phila., 2d series, Vol. V,p. 207, 



PI. 31, Fig. 276 ; Reeve, Conchologia Iconica, Vol. XVI, 



Unio Plate LXXXIV, Fig. 447, 1868. Described and 



figured from Texas. 



This shell has not been found by us in Arkansas nor have 



we seen more than one specimen, said to have been taken in the 



Ouachita river, near the Indian Territory boundary. If this is 



its real habitat it properly belongs in this list and will, besides, 



be found at other localities within the State of Arkansas. 



Unio subgibbosus Lea. 



Jour. Acad. Nat. Sci. Phila., 2d series. Vol. IV, 1858, 



PI. VI, Fig. 36, p. 53. Described from the Oostanaula 



and Etowah rivers, Floyd county, Georgia. 



In the remarks accompanying this form's characterization 



Mr. Lea says that he has specimens received from Dr. Hale, 



from the Red river, Arkansas. On this statement the shell is 



