4ir) ENEMIES OF MOLLUSC A — MAMMALIA. 
otlier classes of the aiiiiiial and vegetable kingdoms, displaying the 
unity of the plan for the diffusion of organic life over the globe and 
emphasizing the reality and truth of the extinction of the weaker and 
more primitive races or their expulsion from those countries adjacent 
to the evolutionary area by the later developed and more adaptable 
races as already described under geographical distribution. 
The earlier deposits contain fossilized remains of species or genera 
wholly extinct at the present day or now living only in inclement 
regions or in countries far distant from the regions in which they 
formerly existed. In the later rocks the number of such forms steadily 
diminish, and the area of their present distribution becomes less and 
less distant from the creative centre, the species gradually approxi- 
mating to, and eventually becoming absolutely identical with, the 
present inhabitants of the district where the fossilized remains are 
found. 
The Enemies of the mollusca are very numerous, as they constitute 
a favourite and nourishing food for many animals, their defenceless 
condition and sluggish movements rendering them an easy prey to 
many creatures besides man, their only i)rotection being the di.staste- 
fulness of certain species, or their power of concealment, as their shell 
only affords protection against their weaker or less astute enemies. 
The Mammalia are very destructive to the molluscan life, more 
especially during the oft-recurring periods of scarcity of their accus- 
tomed food. 
The Hats in this country destroy and devour large numbers of 
Ilelir IT. neinoraUs, etc., this being evidenced by the large 
number of their broken shells strewn about their holes ; in winter, 
they laboriously dig up from their concealment in the ground the 
hybernating or aestivating mollusks, whose whereabouts they have 
detected, and have even been observed to ascend hollyhocks and other 
plants and bring down to their holes for food the IleUx aspersa 
infesting them, the broken shells, the relics of the feast, being left 
strewn about their retreats. 
In Australia the Bush Rat {Mas arboricola Mad.) shows the same 
predilection, and destroys large numbers of the Helix aspersa which 
live in the Botanic Gardens at Sydney, always accompli, shing this 
purpose by breaking in at the apex of the .shell. 
The Voles generally, prey upon the mollu.sca, the Bank Vole evinc- 
ing a predilection for Helix fusca, though also destroying other species. 
