72 



( 'ittcinnati Society of Natural History. 



or the following, so far as the most carefully-made dissections 

 of freshly-collected material will show. 



29. Z. indentatus Say typus. This species occurs here some- 

 what sparingly, under rocks, and occasionally in damp places, 

 under bits of bark and wood. It exhibits no marked varia- 

 tion from types of the species as found elsewhere. 



30. Z. indentatus f umbilicate var. It only remains to add 

 to what was said under Z. sailptilis that this form occurs in 

 the moss on boulders, and in leaves, and is very rare. 



31. Z. Elliotti Redf. This species occurs here, always in 

 rotting logs, or in rotten wood. The structure of the shell, 

 the texture and color and the lingual dentition would rather 

 ally this species with Selenites. The presence of a dart sac 

 is no reason for putting it with Zonites. I believe it should 

 be removed from the Zonitinee altogether, and I think it will 

 be. It is, at least, a transition form. This shell is destroyed 

 by a parasitic larva, the imago of which is a small and active 

 species of Diptera. The grown larva occupies the shell as a 

 pupa house after devouring the inmate. I have noticed this 

 habit of the Diptera in the case of but one other species, and 

 that is P. fastigans Say. At the only locality where I have 

 collected this latter species, more than half the snails were 

 affected, and the numbers of dead shells holding the empty 

 pupa cases, were sufficient testimony to the activity of the 

 parasite. 



In writing up the characters which the shell of this species 

 presents, I call attention to its wrinkled surface, to its dense 

 and horny texture, and especially to the form of the last whorl 

 and of the aperture, and to the marginal thickening of the 

 peristome. These characters should have more weight in 

 classification than a dart sac, which may occur in Selenites as 

 well as Zonites, or the presence of true laterals, not always 

 present in Zonites. This shell, in fact, is one of those forms 

 that the systematists should make most of, for their own 

 safety! 



32. Z. arboreus Say. This species occurs here, as elsewhere, 

 under bark of rotting logs, and exhibits no special characters 

 worthy of note. 



33. Z. radiatulus Alder. This shell is found here in damp 

 woods, among the leaves, somewhat sparingly, many of the 



