Prof. A. Neliring on Myodes lemmus crassidens. 295 



these lemmings beside that of an Arvicola amphibius or 

 A. ratticeps in order to appreciate the great difference. 



Fig. 1. 



yn. 1 



■V1\ 1 



•VnS 



Fiff. 2. 



Fig. 1. — The masticatory surfaces of the cheek-teeth of Myodes lemmus 

 ci-assidens from Portugal, enlarged about 6 times. 



u. Lower row of teeth. o. Upper row of teeth. 



Fig. 2. — The masticatory surfaces of the cheek-teeth of Arvicola ratticeps, 

 K. & BI., from Northern Russia, enlarged 6 times. 



M. Lower row of teeth. o. Upper row of teeth. 



Fig. 3. 



The skull of 3Iyodes lemmus a-assidens, with the under jaw, 

 from Portugal. Natural size. 



The differences between the three known species of lemmings 

 lie chiefly in the colour of the fur and in their size. From my 



