THE NAUTILUS. 103 



But above all, the confusion concerning his Unio cor is the 

 greatest, for there is not the slightest doubt that Mr. Conrad 

 described one species, and figured an entirely different one 

 under this name ! 



Through the kindness of Mr. E. C. Vanatta, of the Academy 

 of Natural Sciences, this confusion has been cleared up. 



Mr. Conrad published, in January 1834, a shell he called 

 Unio mytilloides (Am. Jl. Sci. xxv, pi. 1, fig. 7), and his figure 

 of Unio cor (New Fresh Water Shells, plate iii, fig. 3) in May, 

 1834. These figures were assumed by Mr. C. T. Simpson, to 

 represent the same species. There is little doubt but that the 

 "Mytilloides" figured is a Unio ebenus Lea, and the figure of 

 cor, is much like it, yet not identical. 



No shell exactly like Conrad's cor has yet been obtainable, and 

 if the figure is accurate, the species is probably yet undescribed. 



The true Cor, however, is well characterized, and the type, 

 in the collection ofthe Academy of Natural Sciences, is figured 

 herewith (pi. iii, figs. 1, 2, 3) through the courtesy of Dr. 

 Pilsbry. ' 



U. cor Conrad is a native of the Elk and Flint Rivers. These 

 are tributaries of the Tennessee River. The Unio lewisi, and 

 U. crapulus, of Lea, with which U. cor- has hitherto been identi- 

 fied, come from a different drainage system. 



The true Unio cor is characterized by Mr. Conrad, as having 

 rays, the young, beautifully rayed, and having a sulcus from 

 the beak to base. Neither of which are ever exhibited by 

 lewisi, nor are indicated upon the psendo-figure of cor. Mr. 

 Conrad says the young shells resemble the undatus, Barnes, 

 ( Mr. Conrad's conception of undatus, was the obliquvs of 

 Lamark) . 



The true U. cm' is to be found in many collections, under 

 other names, among which the writer has noted U. edgarianus, 

 tuscumbiensis, andersonensis, and others. The figure of anderso- 

 nensis Lea represents an old, much inflated specimen, rather 

 short behind, but otherwise quite characteristic. 



1 Dr. Pilsbry believes that Conrad's figure, pi. 3, fig. 3, represents the shell 

 he described as Unio cor, and that it was a slightly older specimen than that 

 now figured, but of the same species. 



