54 Trans. Acad. Sci. of St. Louis. 



Unio trapezoides Lea. 



Trans. Am. Philos. Soc, Vol. IV, 1830, p. 69, PI. Ill, 



Fig. 1 ; Reeve, Conchologia Iconica, Vol. XVI, Unio 

 Plate V, Fig. 17, 1864. Described from Lake St. Joseph, 

 Louisiana. 



Unio interruptus Say . Transylvania Journal of Medi- 

 cine, Vol. IV, p. 525, 1831 ; also American Conchology, 

 1832, PL XXXIII. From Bayou Teche, Louisiana. 



Unio alromarginatus Lea. Trans. Am. Philos. Soc, 

 Vol. VIII, 1840, p. 207, PI. XIII, Fig. 21. From the 

 Chattahoochee river. Georgia. Evidently a junior. 



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

 VIII, 1840, p. 217, PI. XVI, Fig. 33. From the Chat- 

 tahoochee river, Georgia. 

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

 burg, at which point very large and fine specimens were 

 secured. It also occurred in the White river, at Augusta, 

 where a single valve was found on the bank ; in the Saline, at 

 Benton ; and in the Ouachita, at Malvern. 



I am not sure that Lea's alromarginatus falls into the 

 synonymy of his trapezoides but it appears to do so judging 

 from the only specimens which have come to notice. From 

 Louisiana come very numerous and fine specimens of this 

 species, but they do not attain the great dimensions reached 

 by the shells from the St. Francis. The species is a mud- 

 loving one, and delights in sluggishly flowing water. The 

 general transverse form, and the peculiar folds or plications 

 on the posterior margin and slope, will serve to distinguish 

 this species from all others. 



Unio trigonus Lea. 



Trans. Am. Philos. Soc.,Vol. IV, 1831, p. 110, PI. XVI, 

 Fig. 40; so, also, Reeve, Concholgia Iconica, Vol. XVI, 

 C7"mo Plate LXXXVI, Fig, 459. From the Ohio river. 



Unio chunii Lea. Jour. Acad. Nat. Sci. Phila., Vol. 

 V, 1862, p. 196, PI. XXVII, Fig. 265. From Dallas, 

 Texas. 



Unio riddellii Lea. Jour. Acad. Nat. Sci. Phila., Vol. 

 V, 1862, pp. 197-8, PI. XXVII, Fig. 267; Reeve, Con- 



