North American Helicidce. 31 



umbilicus is entirely closed, and at the base the spiral impressed 

 lines are more distinct, in which respect it agrees with H. clausa 

 var, suhaTbolabris^ to which I have already referred. 



In //. clausa the umbilical region is more widely excavated, 

 and the groove, behind the reflected lip, producing the con- 

 traction of the aperture, is continued at the base of the shell, 

 becoming wider as it joins the umbilical opening. In II. Mitch- 

 elliana the groove is almost obliterated at the point of reflection 

 of the lip over the umbilicus, by the more tumid character of 

 the last whorl. 



All the specimens in my cabinet of II. MitchelUana are from 

 Ohio. 



The size is somewhat variable. I add the measurements of 

 the largest and smallest individuals : — 



Diam. maj. 17, min. 14, Alt. 9^, mill. 

 " " 15, " 13, " 9 " 



Helix jejHMa Say. 



Synonymy. 



YLqW-s. jejuna Say Jour. Acad. N. Sci. Pbila. II. p. 158, 182L 



Mohiliana Lea Proc Am. PhiL Soc 11. p. 82, 1841. 



" » Obs. IV. p. 17. 



jejuna Be Kay N. Y. Moll. p. 46, 1843. 



Mohiliana Pfr. Mon. L No. 844, 1848. 



" Binney Terr. Moll. II. p. 172, pi. 42, jBg. 2, 1851. 



jejuna W. G. Binney Reprint Say's Descr. p. 19, 1856. 



Say's description is as follows : — 



"Helix jejuna. 



"Shell subglobular, glabrous, pale reddish brown; volutions five, 

 slightly wrinkled, regularly rounded ; spire convex ; suture rather 

 deeply impressed ; aperture dilate lunate ; labrum a little incrassated 

 within, not reflected; umbilicus open, smalL 



