56 Trans. Acad, Sci. of St. Louis. 



the Tennessee drainage of north Alabama and east Tennessee. 

 It is a very tumid shell and bears some points of resemblance 

 to Unio trigonus Lea, but is abundantly rayed over the whole 

 disk, and is of a honey yellow color. 



Unio undulatus Barnes. 



Am. Jour. Sci. and Arts, 1st series, Vol. VI, p. 120, 

 Fig. 2, 1823; Reeve, Conchologia Iconica, Vol. XVI, PI. 

 IV, Fig. 16, as Unio costatus Rafinesque. Described 

 from Ohio. 



Unio latecostatus Lea. Trans. Am. Philos Soc, Vol. 

 X, 1845, p. 68, PI. I, Fig. 2. Described from the 

 Black Warrior river, at Tuscaloosa, Alabama. 



Unio atrocostatus Lea. Trans. Am. Philos. Soc, Vol. 

 X, 1845, p. 70, PI. II, Fig. 5 ; Reeves figure 404, Con- 

 chologia Iconica Vol. XVI, Unio Plate LXXVII is of 

 pUcatus and not of this shell at all. 



Unio quintardii Cragin. Bull. Washburn Coll. Lab'y 

 of Nat. Hist. Vol. II, p, 6, 1887. From Salt Creek. 

 Indian Territory, Sac and Fox Reservation. 



Unio pilsbryiMarah. Nautilus, Vol. V. May, 1891, p. 

 1; illustrated in The Nautilus, Vol. VII, No. 1, May, 

 1893, PI. I, Figs. 7 and 8. Described from the Little 

 Red river, Arkansas. Inspection both of the types, and 

 the published figures confirms this disposition of the 

 form. 

 Specimens were observed on the bars of the Saline river, at 

 Benton. It occurs commonly in the Little Red river, near 

 Clinton, Van Buren county, from which locality came the 

 shells that were characterized by the name of Unio pilsbryi. 

 The species is of wide distribution, ranging from New York to 

 Kansas, Nebraska, Dakota, and to west Central Texas; east to 

 Georgia, Alabama, and intermediate States. It is flatter than 

 Unio plicatus, and the undulations are differently disposed; 

 they are commonly more numerous than inLesueuer's species, 

 and often are interrupted or broken ; not infrequently speci- 

 mens are found in which the undulations cover the entire disk, 

 at other times they are few in number, and almost entirely 

 confined to the posterior slope. This is one of the most 



