ertiary this continent was connected by land to the
northwest with Asia, and to the northeast, through Greenland and
Iceland, with western Europe.

The distinction between the two groups is well marked. All the
_Mazama_ type are without a true brow-tine to the antlers; the
lower ends of the lateral metacarpals only remain; the vertical plate of
the vomer extends downward and completely separates the hind part of the
nasal chamber into two compartments; and with hardly an exception they
have a large gland on the inside of the tarsus, or heel. The complete
development of these characters is exhibited in northern species, and it
has been beautifully shown that as we go southward there is a strong
tendency to diminished size; toward smaller antlers and reduction in the
number of tines; to smaller size, and finally complete loss of the
metatarsal gland on the outside of the hind leg; and to the assumption
of a uniform color throughout the year, instead of a seasonal change.

The two styles of antler which we recognize in the North American deer
are too well known to require description. That characterizing the mule
deer (_Mazama hemionus_) and the Columbia black-tailed deer
(_M. columbiana_), seems never to have occurred in the east, nor
south much beyond the Mexican border, and these deer have varied little
except in size, although three subspecies have lately been set off from
the mule deer in the extreme southwest.

The section represented by _M. virginiana,_ with antlers curving
forward and tines projecting from its hinder border, takes practically
the whole of America in its range, and under the law of variation which
has been stated, has proved a veritable gold mine to the makers of
names. At present it is utterly useless to attempt to determine which of
the forms described will stand the scrutiny of the future, and no more
will be attempted here than to state the present gross contents of
cervine literature. The sub-genus _Dorcelaphus_ contains all the
forms of the United States; of these, the deer belonging east of the
Missouri River, those from the great plains to the Pacific, those along
the Rio Grande in Texas and Mexico, those of Florida, and those again of
Sonora, are each rated as sub-species of _virginiana_; to which we
must add six more, ranging from Mexico to Bolivia. One full species,
_M. truei,_ has been described from Central America, and another
rather anomalous creature (_M. crookii_), resembling both