MAMMALS OF MINNESOTA. 221 
. bordering upon the Mississippi river except southwardly, where 
a variety of our common Geomys bursarius extends into Florida 
and Georgia and was the first of the family found in the United 
States though a different species was previously noticed in 
Mexico. The northern limits of the family are determined by 
the frosts of winter, for burrowing becomes an arduous task 
where much of the time the soil is frozen six or more feet deep. 
In the New England and Middle States the family is entirely 
absent. 
These low-bodied, dense-furred animals are chiefly remarka- 
ble for the large fur-lined pockets extending from the shoulder 
to the sides of the mouth and opening entirely outside the 
buccal cavity. The pockets have several special muscles to 
retain them in place. The pockets are used for carrying food, 
which in all the species, is stored in subterranean graneries 
against time of drought or winter frosts. Considerable skill is 
shown in collecting the proper amount in one place, so that 
the heat generated ina mass of grass, for example, shall be 
enough to cause the growth of fresh shoots but not enough to 
destroy the whole. 
As now understood the pocket-gophers constitute a well cir- 
cumscribed family of two genera, allied, on the one hand, to 
the field mice (Arvicolide) by many important cranial and 
other characters and, on the other to the pouched mice (Saccom- 
-yidc) by the possession of fur-lined pouches on either side of 
the mouth (but having no connection with the mucous surfaces). 
Again, the gophers are allied by quite unmistakable points of 
agreement with the African mole rats (Georychide) which in 
habits they more resemble than either of the above families. If 
it were pertinent insucha work as this to discuss the relative 
value of these different affinities, it might be shown that a very 
good case could be made in favor of a closer relationship with the 
Georychide or Muride than with the Saccomyide. After a 
comparison of cranial characters between Fiber the Sac- 
comyidee and Geomys it seems well to suggest that the presence 
oz absence of external pockets ought not to be too implicitly 
relied upon in collocating the families of rodents. 
It is only safe to say at present that the Geomyide constitute 
a distinct family of myomorphic rodents with uncertain inter- 
ordinal affinities. No definition of the family is necessary in 
this connection, but the student is referred to the following 
papers on the group: 
