18 Trans. Acad. Sci. of St. Louis. 



The geographical range of this form is from western New 

 York to Minnesota and Kansas, south to Texas, and east 

 to Georgia. In the Mississippi and Cumberland rivers it is 

 both abundant and variable. There are few shells among the 

 Unionidce that present so great a range of variation as this one. 



Unio glans Lea. 



Trans. Am. Philos. Soc, Vol. IV, 1830, p. 82, PL VIII, 

 Fig. 12. From the Ohio river ; Conrad's Monograph, PL 

 IX, Fig. 2, 1836. 



Unio pullus Conrad. Monograph of Unio, 1838, p. 

 100, PL LIV, Fig 2. From the Wateree river, South 

 Carolina. 



Unio granulatus Lea. 1861. Jour. Acad. Nat. Sci. 

 Phila., Vol. VI, 2d series, 1866, p. 48, PL XVI, Fig. 46. 

 Big Prairie creek, Alabama. 



Unio germanus Lea. 1861. Jour. Acad. Nat. Sci. 

 Phila., Vol. VI, 1866, p. 49, PL XIX, Fig. 54. From 

 Coosa river, Alabama. 



Unio cromwellii Lea. 1865. Jour. Acad. Nat. Sci. 

 Phila., 2d series, Vol. VI, 1868, p. 258, PL XXXI, Fig. 

 73. From Kiokee creek, Albany, Georgia. 



Unio cylindrellus Lea. Jour. Acad. Nat. Sci. Phila. 

 1868, 2d series, Vol. VI, p. 308, PL XLVIII, Fig. 121. 

 From Tennessee, north Georgia, and north Alabama. 



Unio corvunculus Lea. Jour. Acad. Nat. Sci. Phila., 

 2d series, 1868, Vol. VI, p. 314, PL L, Fig. 127. From 

 Swamp creek, Whitfield county, Georgia. 

 The localities at which this species has occurred, in collect- 

 ing in Arkansas, are all in Carroll county, and presumably from 

 the same portions of the White river. The three specimens 

 submitted were kindly furnished by Mr. F. A. Sampson, of 

 Sedalia, Missouri, by whom they were collected. The synonymy 

 indicated above is based upon very large series of specimens 

 which comprise materials from every one of Lea's localities. 

 The species was also figured by Reeve, in 1868, Unio Plate 

 XXXVI, Fig. 190. The specimen figured by him shows the 

 emarginate character of the female, which sex he had before 

 him. The shell is usually abundant in warm, shallow water, 



