316 GEOGRAPHICAL LIMITATIONS.—COAST. 
of the causes of a great number of now unexplained 
facts; for the three kingdoms of nature are not merely 
associated, but intimately connected, and since 
secondary causes have so great influence on animal 
and vegetable dispersion, we may not unfrequently 
discover the cause of distribution of these to rest 
with the qualities of the soil on which they are 
maintained,and still more frequently the phenomena 
of animal distribution to depend on the nature of 
certain vegetable products occurring on the spot, 
or diffused over those tracts to which certain animal 
forms are peculiar. Again, the selection of par- 
ticular food by certain of the carnivorous animals 
will in a great number of instances determine with 
exactness the limits of such species. 
We now pass on to consider the third division of 
the subject, the shore and marine productions of 
South Devon, subjects in a great measure apart from 
those first discussed ; and although we found it con- 
venient to consider the Fauna of Dartmoor, and 
that of the cultivated districts separately, the 
productions of those spots are not so distinct or 
peculiar as we shall find those of the shores and sea. 
Divisions of this kind arbitrary as they are, will 
nevertheless be found useful, because as the qualli- 
ties of the elements and constitution of the climate 
in each may be expected to differ, it might be also 
ascertained that the tribes of creatures inhabiting 
or frequenting them were more or less classified or 
brought together by reason of those influences. It is 
farther convenient for the purpose of comparison 
with other spots of similar or dissimilar natures. 
We must in the first place say a few words on the 
Mammalia. 
