vol. xx. (2) FRESH-WATER MOLLUSCA OF GLOUCESTERSHIRE 145 
These examples tend to support the view held by many that 
relatively unimportant features are transmissible, and in the 
course of time become fixed. 
STENOGYRID#:. 
Azeca tridens (Pulteney) . The type-form seems to be very 
scarce in England, the common one being the variety known 
as A. tridens var. nouletiana, Dupuy, the difference being 
that the type-form has a small tooth or projection just within the 
lip of the shell which is not found in the variety. There is 
another variety known as A. tridens var. alzenensis, Dupuy, 
which has in addition to the denticle in the type-form two 
further denticles situated some distance within the mouth of 
the shell. All three forms occur amongst the numerous 
specimens which I have from Frocester, so that in addition to 
the type-form we have in this county the two following named 
varieties: Azeca tridens var. nouletiana, Dupuy, and A. 
tridens var. alzenensis, Dupuy. 
Two other modifications which do not appear to have been 
given varietal names also occur at Cranham. 
VERTIGINIDAE. 
Vertigo minutissima (Hartmann). In compiling my 
previous lists I regret I overlooked a notice of this species, 
which has been found at Clifton, and is recorded by Dr. J. W. 
Williams in the Journal of Conchology, vol. v., p. 357. 
CLAUSILIIDAE. 
Glausilia bidentata var. albida, Jeffreys. During the past 
summer I took two specimens of this very scarce form at Bredon, 
which lies just outside the county boundary. Although not 
strictly a Gloucestershire shell, it seemed desirable to refer to 
it on account of its rarity. 
LIMNAlID/E. 
Limnasa auricularia var. reflexa, Nelson. A considerable 
number of this interesting variety was taken during the early 
summer of 1918 in the canal near Hempstead. In 1919 a 
