LYMNyEHLE OF NORTH AMERICA. 321 



a shell is found in the autotypes of desidiosa in the Philadelphia Acad- 

 emy and this type of shell occurs in 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. 



Desidiosa, then, differs from obrussa (desidiosa of authors; in 

 its generally larger and more solid shell, longer and more turreted 

 spire, more pronounced and heavier sculpture and more convex whorls, 

 with deeper sutures ; in having a distinct internal rib inside the outer 

 lip and in the presence of a fold on the columella. Compared with 

 palustris, desidiosa is smaller, usually more solid and with a more 

 obese body-iL'horl and a more dilated aperture. The spire, too, is more 

 sharply conic and the whorls are more tightly coiled, producing a deeper 

 suture. The inner lip is also more expanded, producing a heavier 

 callus. The shells called elodes by Say are larger, more flat-sided, with 

 a longer spire, and the whorls are not so rounded and are more oblique. 

 If we accept the evidence afforded by Say's specimens, and there seems 

 to the writer to be no other course, then the shells usually called de- 

 sidiosa must bear the name of obrussa, which is the first available name, 

 and the name desidiosa must be used for the shells so called by Say. 



There is some variation among the specimens referred to desidiosa, 

 especially in the lot from the small stream near the Erie Canal, but 

 all have the peculiar pot-bellied aspect of the body whorl, so markedly 

 emphasized in Say's figure (pi. XXXIV, figs. 8-9). Specimens from 

 Seneca Lake vary toward palustris alpenensis (pi. XXXIV, figs. 10- 

 12 J. Desidiosa appears to be a depauperate variety of palustris. 



Galba palustris blatchleyi Nov. Var. Plate XXXIII, figures 

 34-36. 



Limncsa palustris michigaiieusis Blatchley and Daxiels (non Walker), 

 27 An. Rep. Dept. of Geol and. Nat. Res. Ind., 1902, p. 596, 1903 (part).— Dan- 

 iels, 1. c, p. 636, 1903 (part). 



Shell : Elongated, rather solid, periostracum very light-yellowish 

 horn; surface polished; sculpture as in palustris; whorls 6 to 6^, 

 rounded, the body whorl subglobose ; spire acute, longer than the aper- 

 ture; sutures well impressed; aperture long-oval; outer lip with heavy 

 internal varix ; inner lip narrow, triangular, either tightly appressed 

 to the columellar region and forming a plait or broadly reflected and 

 leaving a narrow chink; axis twisted. 



Length. Breadth. Aperture length. Width. 



20.00 8.00 8.50 4.00 mill. Types 



17.00 8.25 7.75 4.00 " 



16.50 7.00 8.00 3.80 " 



16.50 7.00 7.60 3.50 " 



