198 PNEUMONOBRANCHIATA. 



Cochlodonta secale. Fer. Prod. 64. 



Inhab. roots of trees and under stones, in chalky 

 districts, and cracks in rocks in oolite limestone. 



Animal blackish brown, warty, foot slender. 



Shell a quarter of an inch or rather more in length, 

 of a greyish brown colour, opake, obliquely striate 

 longitudinally; spire composed of eight or nine 

 rounded volutions; aperture with seven or eight 

 laminar teeth, two on the pillar lip; three on the 

 outer lip, including the central one, all of which are 

 visible on the back in the appearance of three pale 

 bands ; and two on the interrupted part of the peri- 

 stome, the outer one of which is more prominent 

 and close to the margin, with often a tubercle on its 

 outside. 



The shell of the young animal is clothed with an 

 earthy covering, like Bulimus obscurus. In this state 

 it is described by Miiller, according to Jeffreys, un- 

 der the name of Helix ventricosa. 



Montagu (T. B. 340.) truly observes, that "these 

 projections, usually called teeth, are not properly den- 

 ticles or tooth-shaped protuberances, but are fine 

 white laminae or ridges running spirally backwards in a 

 parallel direction to each other ; those on the exterior 

 lip may in most instances be traced through the 

 outside of the shell," they are in fact foldings in of the 

 substance of the shell, caused by some withdrawing 

 of the mantle of the animal in the part immediately in 

 connection with them ; this is also the case with many 

 of the foreign "toothed" Helices (Helicodontce) . The 

 true teeth must be formed nearly in the same way, but 

 they are produced by repeated deposits of layers of 

 calcareous matter, one over the other, to fill up the 

 cavity as the mantle is withdrawn : while these plaits 



