22 THE NAUTILUS. 



Say's figure in the American Conchology (plate 55, fig. 3) cor- 

 responds with the specimens from Williauisville, all having the 

 peculiar obese body whorl. Say himself identifies desidiosa from 

 western New York in Long's expedition, II, p. 263, where he says, 

 '' Lymneus desidiosus nob. Falls of Niagara." 



The history of desidiosa in the American monographs is interesting 

 and clearly indicates that since Say's time little attention has been 

 given to closely analyzing this species. In all of his references Say 

 distinctly indicates a shell of the palustris type. 



Haldeman describes and figures the form now distinguished as 

 obrussa and not the true desidiosa (compare his plate with Say's 

 figure 3). Many of Haldeman's figures are abnormal and do not 

 represent obrussa as it is usually developed. Tryon, in his contin- 

 uation of Haldeman's work, (p. 104) states' that many of the figures 

 on this plate are not desidiosa but a form of columella (inacrostoma). 

 In this statement Tryon is wrong and could scarcely have seen 

 Haldeman's specimens, for a recent examination proved them all to 

 be referable to obrussa (desidiosa of authors) although as stated 

 above several of the specimens are abnormal. The writer has col- 

 lected many specimens similar to those figured on Haldeman's plate. 



Binney, in his Land and Fresh-water Shells of North America, 

 Part II, makes obrussa a synonym of desidiosa, thus showing that 

 he considered the latter the small, smooth form and not the true 

 desidiosa of Say and his figure 68 is questionable for the reason and 

 is probably of a long-spired obrussa. In Baker's Mollusca of the 

 Chicago Area obrussa is described and figured as desidiosa. 



Recently Dr. -W. H. Ball, in his Alaska Mollusks (p. 73, fig. 51) 

 figures Say's obrussa under desidiosa, but also refers in his synonymy 

 to Binney's figure 68. The European monographs have given 

 figures referable to obrussa rather than to desidiosa. 



Amidst the uncertainties caused by the absence of Say's types we 

 must look for a shell which is closely allied to elodes, but is smaller, 

 with more convex whorls, and possesses 5 instead of 6 full whorls. 

 Such a shell is found in the autotypes of desidiosa in the Philadel- 

 phia Academy, and this type of shell occurs in several localities in 

 the eastern part of the United States, and is easily separable from 

 any other known species or variety. The spire varies considerably, 

 being short, or long, or even scalariform. There are from 2 to 5 

 rest varices on the whorls. 



