72 



The branch of sniils under the family head of 

 Zonites are thus, without a single exception, found in 

 the immediate neighbourhood of Nottingham. 



Helix. 



This is a spiral shell, having a lunate aperture, 

 which is thickened, and the peristome mostly reflexed. 

 It is chiefly stout and opaque, occasionally, however, 

 being semitransparent and thin. Generally globose. 



The animal is tolerably large for the size of the shell. 

 There are four tentacles. The tail is pointed, and the 

 foot frequently large. The mantle does not cover the 

 edge of the mouth. 



Some of the species are vrell known to every one, 

 owing to their size, abundance, and habits. 



The Helix tribe vary from that of the Zonites chiefly 

 in the edge of the mouth. In the former it is thick- 

 ened, and the peristome mostly reflexed, whilst in the 

 latter the edge is ihin and the peristome not reflexed. 

 The Helix is for the most part more solid, more 

 opaque, more globular, and has not so glossy an 

 appearance. 



The animal varies in the form of the tail, that of the 

 Helix being lanceolate, whilst in the Zonites it is 

 truncate. 



Professor Forbes remarks that the edge- tooth of the 

 tongue of the Zonites is aculeate, whilst that of Helix 

 is serrated. 



