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XXI. — Description of a Species of Arvicola common 
in Aberdeenshire, 
By Mr W. Macgillivray, M. W. S. 
(Read 1st May 1830.; 
The mammiferous land animals of Great Britain might na- 
turally be supposed to have received abundant notice, and 
the more so in proportion to their paucity and their import- 
ance in the scale of creation. That this, however, is not 
the case, is notorious. The more common mammiferous ani- 
mals are indeed known to us by name, but while each of 
these might form the subject of an extended memoir, we 
have as yet only brief and unsatisfactory notices respecting 
them. But novelties may yet be found ; and it is hardly 
necessary for me to oifer an apology for requesting a mo- 
ment's atttention, while I lay before the Society an account 
of a new species of Arvicola, whose habits I have had 
opportunities of observing for several years. 
The animal in question is very common in many parts of 
the counties of Aberdeen and Banff, where, among the 
Yulgar, it bears the names of Black Dog and Water Dog. 
