48 ZONITID. 
to be constant, and therefore diagnostic, is that the 
umbilicus of a//iavia expands with its growth, while that 
of helvetica contracts, so that in full grown specimens of 
helvetica the last whorl hides the penultimate when viewed 
from beneath, which is never the case with a//zaria. ‘The 
garlic smell of a//iaria I have very often observed in 
helvetica, and alliaria is occasionally without it. 
But it is rather with ce//avza that the confusion is likely 
to arise. Helvetica is more glossy (in fact it is the most 
glossy of all our British’ species) ; its form more globose 
and compact, the sculpture almost absent, and the spire 
usually more raised and pointed. Unlike Aelvetica, 
cellaria always leaves the penultimate whorl exposed 
when viewed from beneath; and the suture of cellaria 
is broader and deeper. The colour is not much to rely 
on, but usually that of /elvetica is darker and clearer 
than that of cel/aria. 
Mr. E. Collier of Manchester was the first to call my 
attention to the fact that this species will completely 
clean out other small shells when put into a box with it. 
He instanced H. fulva which was completely cleaned 
out by this means. I have since observed the same 
cannibalism in A. ztidula; Helix rotundata and V. 
pellucida when placed in a tube with the above, fall an 
easy prey, the shells being beautifully cleaned. 
Var. viridans (Cockl). Greenish white. 
