42 Trans. Acad. JScL of St. Louis. 



Fig. 450, 1868. Described from the Alabama river, at 

 Claiborne. 



Unio vallatus Lea. Jour. Acad. Nat. Sci. Phila., 2d 

 series, Vol. VI, 1868, p. 315, PI. L, Fig. 128. De- 

 scribed from Alabama. 



Unio refulgens Lea. Jour. Acad. Nat. Sci. Phila., 2d 

 series. Vol. VI. 1868, p. 317, PI. LI, Fig. 130. De- 

 scribed from Lauderdale county, Mississippi. Plate 

 XV, Figs. 3-4, herein. 



Unio sphcericus Lea. Jour. Acad. Nat. Sci, Phila., 2d 

 series, 1868, Vol. VI, p. 319, PI. LI, Fig. 132. De- 

 scribed from the Pearl river, Mississippi. 



Unio cahabensis Lea. Jour. Acad. Nat. Sci. Phila., 2d 

 series. Vol. VIII, 1874, p. 17, Pl.V, Fig. 14. Described 

 in 1871 from the Cahaba river, Alabama. 

 This is an abundant form in the St. Francis, at Wittsburg, 

 and a common one in the Saline, at Benton. It is, no doubt, 

 quite generally distributed over the State, and the various 

 names above listed are represented by many of the varying 

 forms which the species exhibits. It will be noticed, in the 

 above synonymy, that several of the so-called species come 

 from the same stream or drainage area, and their descriptions 

 are separated from one another by the interval of a few 

 years. Specimens of every form listed in this synonomy, 

 Lea's species all having been named by himself, have been 

 seen and studied in the course of the past ten years. With 

 the exception of Unio iurgidus Lea examples of every species 

 is before the writer at this time. No hesitation is felt in 

 regarding this series of forms as one species, varying only in 

 those trivial matters which should not, at most, constitute 

 varietal value and which are the expression of different 

 geographic factors. 



The plates given herein show certain of the forms of this 

 widely distributed shell, in some of its most marked phases. 

 Recently, from Louisiana comes a form of pustulosus that is 

 very like sphcericus, as it is found in Texas ; from the Ouachita, 

 at Arkadelphia, come excellent specimens of refulgens which, 

 in large series, approach the Louisiana forms. The St. Francis 

 river presents the typical specific form, and with it sphcericus 



