MONOGRAPH OF THE MICROTINJi 



I. STRUCTURE AND CLASSIFICATION 

 a. Introduction. 



The Voles and Lemmings are SimpHcidentate Rodents 

 belonging to the great family Muridae, of which they constitute 

 a subfamily, the Microtinaj. They are very widely distributed, 

 ranging throughout the Holarctic region from the limits of 

 terrestrial mammalian life in the high north southwards to the 

 Alpine meadows of the mountains of Guatemala (just within the 

 Neotropical region) and to those of Yunnan and Burma (in the 

 Oriental region). They are not, however, known to live in 

 Northern Africa, although a species of the fossorial genus Ellobius 

 has left its remains in the Pleistocene deposits of Tunis and 

 Algeria, and members of less highly specialized genera inhabit 

 or have inhabited some of the islands of the Mediterranean. The 

 vertical range of the subfamily is also wide, extending from the 

 sea-beach up to the limits of mammalian life, at altitudes of about 

 20,000 feet in the Himalayas. 



The oldest forms yet discovered are found in the later Pliocene 

 deposits in Europe, and are already fully developed voles. Not 

 improbably the Microtinse originated in early Tertiary times in 

 Northern and Central Asia, and it is to future palaeontological 

 work in that continent and perhaps in the high north that we must 

 look for information about the forms which once connected the 

 Microtinae with the other subfamilies of Muridse. 



Having regard to the sedentary habits of these rodents and to 

 their wide distribution, it is not surprising to find that the sub- 

 family is a large one, comprising thirty-one genera and several 

 hundred species. Within rather narrow limits the species show 

 considerable plasticity, developing numerous more or less well- 

 marked geographical or purely local races to meet the exigencies 

 of the environment. They have therefore attracted a great deal 

 of attention from systematists, and a very large number of 

 generic, subgeneric, specific and subspeciflc names have been 

 bestowed upon them in an extensive and widely scattered 

 literature. In consequence the group has become one of the 

 most difficult to deal with from a systematic point of view. Quite 

 apart from this, however, many of the most important and most 



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