RODENTIA. 373 



steppes and east of the Volga, wandered as far as the extreme 

 west of Europe, where it was hunted by the Palaeolithic men in 

 France ; and one portion of skull has been discovered in the 

 Thames valley-gravels near Twickenham. 



Nothing of importance is known concerning the ancestry of 

 the sheep and goats ; but the closely -allied musk ox (Ovibos 

 moschatus), now confined to the Arctic regions, is interesting 

 as being represented by various characteristic remains in the 

 Pleistocene deposits of Europe as far south as the Pyrenees 

 and Alps, while allied species occur in Pleistocene formations 

 equally far south in North America. Portions of the skull of 

 the musk ox have been found in the Thames valley, at Fresh- 

 ford near Bath, and also probably in the Cromer Forest Bed. 



The true oxen, so far as known, appear first in the Lower 

 Pliocene of India (Siwalik Formation), and they reach both 

 Europe and North America in the Upper Pliocene. In some 

 of the early species the females seem to have been hornless 

 (Leptobos falconeri from India, L. etruscus and L. elatus from 

 Tuscany, France, and Spain). Other Siwalik species, however, 

 are very closely related to the common domesticated Bos taurus. 

 Bos primigenius, from the Pleistocene of Europe, and probably 

 the Urus of Caesar, seems to have been merely a gigantic race 

 of the existing form just mentioned. The genus Bison is also 

 first represented in the Lower Pliocene (Siwalik Formation) of 

 India; and remains of the extinct forerunners of the North 

 American " buffalo " occur in the Upper Pliocene of the United 

 States. The Bison bonasus, now preserved in Lithuania and 

 the Caucasus, ranged during the Pleistocene period throughout 

 the greater part of Europe; and numerous remains of this 

 animal have been found in England, both in the Cromer Forest 

 Bed and in later Pleistocene deposits. 



ORDER 5. RODENTIA. 



The Rodentia, or gnawing mammals, are a well-defined 

 order of small animals, destitute of canine teeth and one or 

 more of the premolars, but with one of the pairs of chisel-shaped 

 (scalpriform) incisors above and below greatly-enlarged, and 



