JVbrth American Terrestrial Mollusks. 159 



We restrict our corrections and sus^orestions to the g-enera 

 belonging to the fiiuna of North America, exclusive of that 

 of Mexico and Lower California. 



The divisions A and B (p. 2) of Dr. Gray (founded on 

 the head, eye-peduncles and tentacles being retractile under 

 the skin, or contractile) cannot be retained, as the recent 

 observations of Stoliczka have proved the eye-peduncles of 

 Oncliidium to be reall}^ retractile. The same may possibly 

 be true of Veronicella. 



The sections 1, Vermivora and 2, Phyllovora are equally 

 untenable. There is not the difference in food indicated by 

 these names. For instance, no species can be more carnivo- 

 rous than Stenogyra decollaia, which is always placed among 

 the herbivorous genera. Limax maximus, also, we have 

 known to devour its kind, though it is ranked in the same 

 section. The first instance shows how incorrectly the 

 aculeate marginal teeth alone are called of carnivorous type, 

 as they are entirely wanting in 8tenogyra decoUata. 



The presence or absence of a jaw is not a reliable char- 

 acter to sustain the distinction of these sections. Helix 

 incequalis, for instance, has no jaw. 



The teeth are equally unreliable, inasmuch as all our 

 species of 31acrocyclis, placed in section 2, have teeth like 

 those described in section 1. So have Helix incequalis, 

 Hyalina Baudoni and Gonospira j)alanga. Moreover, some 

 genera show a gradual change from the so-called herb- 

 ivorous to the so-called carnivorous type of teeth. Thus in 

 Glandina and Macrocyclis we find the carnivorous ty^Je only ; 

 in Zonites, Vitrina and Limax the marginal teeth are 

 carnivorous, and occupj' the greater part of the membrane, 

 but the few laterals are of the herbivorous type. In Zonites 

 cellarins the latter are greatly* modified and resemble closely 

 the carnivorous type. The membranes of Vitrina limjnda 

 and Zonites cJiersinus, however, by the increased number of 

 laterals and the bifurcation of the marginals, are more nearly 

 related to the herbivorous type. Thus, instead of the differ- 



