318 ARVICOLID^. 



three genera above mentioned, two others, Ascomys and 

 Castor '." 



In the opinion here expressed by our talented friend 

 we fully concur, but as confirmation we may bring before 

 the notice of our readers the existence of a genus of 

 Rodents peculiar to America, in which a Rat-like form 

 and long tail is combined with rootless molars, as in the 

 Voles. It is the genus Neotoma, and is found in the 

 Southern States of North America, and in Central 

 America. But there is one British Rodent even, which 

 may be properly instanced as indicating a passage from 

 the Voles to the true Rats. We allude to the Bank Vole, 

 in which, on reference to the figure, the tail will be seen 

 to be of greater relative length than in the other two 

 species, and with this is associated a somewhat narrower 

 cranium, and molars which become rooted with age, 

 though the roots are never so well developed as in the 

 true Rats or Mice. 



The Water Vole, or, as it is more frequently called, the 

 Water Rat, is found in most parts of Europe, and is too 

 common to require further comment, excepting to men- 

 tion that in certain localities it varies sufficiently from its 

 usual appearance to have led to the belief that it was a 

 distinct species. Thus a small variety from the Alps has 

 been described as A. terrestris, and a pale one from the 

 Pyrenees has been called A. monticola, whilst in our own 

 country, a black variety has received the name of A. ater. 

 In its geographical range, however, the Water Vole is not 

 wholly confined to Europe, but has been met with in 

 China ; in the vicinity of the River Amoor it was found 

 by Dr. Von Schrenck, as we learn from his work on the 

 Mammalia of that district. In this country it is very com- 

 mon ; frequenting the banks of rivers, excavating its habi- 

 tations to a considerable distance, and breeding in these 



