Call — The Unionidce of Arkansas. 15 



In further history of the form it may be stated that the 

 real author of the species was Dr. Hildreth, of Marietta, Ohio, 

 who sent it to Mr. Lea with the manuscript name of Unio 

 coccineus. Hildreth did not describe it under that name, even 

 in manuscript, and Mr. Lea, adopting the proposed name, 

 described the species as new in the Trans. Am. Philos. Soc, 

 Vol. VI, PI. V, Fig. 12, 1834. A good figure may also be 

 found in Conrad's Monograph, PL XIII, Fig. 1. The white- 

 nacred variety is figured by Conrad, on the same plate, under 

 the name of Unio catillus, from the Scioto river, Ohio. 



Unio cylindricus Say. 



Plate XI. 



Unio cylindricus Say, in Nicholson's Encyc. Am. Ed. 

 Article Conchology, PI. 4, Fig. 3, 1816. 



Unio naviformis Lamarck. Deshayes Encyc. Meth. 

 Vers ,Tome II, p. 580, No. 5, 1830. 



Unio naviformis Lamarck. Animaux sans Vertebres, 

 Tome VI, p. 537, No. 20, edition of 1838. From the 

 Ohio. 



Unio cylindricus Say, Barnes, in Am. Jour, of Sci. 

 and Arts, 1st series, Vol. XIV, PI. I, Figs. 13a, 13b. 

 This species is abundant in the St. Francis, Saline, and 

 Ouachita rivers, Arkansas, from which localities many speci- 

 mens have been seen. In the Cumberland and Harpeth rivers 

 of Tennessee, the largest and finest specimens noticed have 

 been taken. In geographical range the species extends from 

 western New York to Indiana, Kansas, and Texas, and south 

 to Central Alabama, in the Alabama river, at Selma. The 

 specimen figured is from the White river, Indiana, and was 

 contributed by Professor Barton W. Evermann. 



Unio donaciformis Lea. 



Trans. Am. Philos. Soc, Vol. Ill, p. 266, PI. IV, 

 Fig. 3, 1827. Described from Ohio. 



Unio zigzag Lea. Trans. Am. Philos. Soc, Vol. Ill, 

 p. 409, PI. XII, Fig. 19, 1829. Described from Ohio. 

 This species is abundant in the St. Francis river, at Witts- 



