ate rd f yy : 
- MAMMALS OF MINNESOTA. 17 




_» The ox is supposed to be derived from three ancient species 
vis (Bos brachyceros, B. primigenius, B. frontosus) which have since 
‘been crossed interminably. While the ox seems to have ap- 
peared in the eastern continent, America may claim to have 
been the birth place of the bison whose enormous herds were 
once so characteristic a feature of our country. Bison latifrons 
_ from the diluvium is the first form known. Allen believes that 
_ from this species have sprung B. antiquus in America and B. 
om priscus in the old world, the precursors of the living species 
i), im éach. 
- -Gne group of mammals—the Cetacea—have left no trace in 
-.the formation of Minnesota. Our knowledge of the whale is a 
rae very recent acquisition and is chiefly derived from the careful 
researches of Eschricht, Brandt, Van Beneden, Gervais and 
_ Flower. Whalebone had long been an article of commerce 
before the relation it sustained to the teeth of other mammals 
ie _/ was made out—that it is, indeed, a thickened appendage to the 
mucus membrane of the mouth, used in straining out of the 
i _. water the minute animals serving its owner for food. The 
discovery that the young or foetal bearded whale has teeth, 
which are never cut, but are soon reabsorbed, deserves to be 
noted here as a remarkable instance of unexpected genealogi- 
cal testimony. We are thus informed that the present whales 
are lineally descended from toothed whales not unlike the 
; _ dolphin. The cetaceans were most plentifully represented in 
_. the Miocene period and at that time the two groups of whales 
me: were less clearly marked. It is certain that the whalebone 
-_-whales are the latest members of the group historically. . The 
- origin of the group is shrouded in mystery, a more or less 
obvious similarity in certain osteological features to the 
omnivorous hoofed animals being the only clue as yet available. 


ee SUB-CLASS MONOTREMATA. 
This sub-class contains the principal orders of mammals and 
all of those included in this work with the exception of the 
opossum, which is the sole North American representative of 
the sub-class Didelphia. The characters of the sub-class, so far 
as here necessary, are the following: Development of the foetus 
is accomplished through the agency of a placenta formed from 
the allantois membrane. The mammary glands have teats. 
ae _ Thereis, in the female, a single vagina. There is no cloaca. 


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