LEMMUS 193 



has given so little help to the systematist and why the species 

 of Lemmus are still so imperfectly understood. 



The described forms fall into two well-marked groups dis- 

 tinguished by the colour-pattern of the dorsal surface. In the 

 first group, characterized by its striking chequered dorsal pattern 

 of intense black and brilliant yellow, there is only a single form, 

 the Norwegian Lemming inhabiting Scandinavia and ranging 

 eastwards to the western shore of the White Sea. The second 

 group, characterized by its more sober, essentially uniform 

 dorsal pattern, variegated at the most by a more or less distinct 

 black dorsal stripe on the head and neck, by an indistinct lateral 

 streak on each side of the head, and by anterior dullness and 

 posterior brightness or intensity of colour, comprises all the 

 remaining eleven forms. Of these, five range vicariously through 

 northern Europe and Asia, from the eastern shore of the White 

 Sea to Kamtschatka, one inhabits the Pribilof Islands, and 

 five the North American continent, ranging from Alaska east- 

 wards to the Cumberland Peninsula, Baffin Land, and south- 

 wards to Alberta and the southern shore of Hudson's Bay. Some 

 of these members of the second group, e.g., L. yuhonensis with 

 its greatly enlarged auditory bullae, L. nigripes with its black 

 feet, and L. o. novosihiricus subject to remarkable seasonal 

 changes (paralleling those normal in Dicrostonyx) in its high 

 northern station, are quite strikingly different from normal 

 L. obensis in certain respects. But in all essential structural 

 characters and in the general colour scheme they are not more 

 widely different, so far as the available material and descriptive 

 literature permit one to form a judgment, from each other and 

 from typical L. obensis than are the subspecies of Microtus 

 agrestis or those of Evotomys rufocanus from each other. 



The latter species affords indeed (as explained below) a very 



i, close analogy to the present case. It is possible that really 



adult material will reveal more important differences between 



j the members of the present group than those now apparent; 



and in the absence of such material I propose to leave things 



I as I find them. But in my opinion it is most probable that 



' all the forms in question will have to be treated as subspecies 



I of L. obensis hereafter, and that we shall revert, with fuller 



I knowledge and no doubt for better reasons, to the views of an 



earUer generation. 



Fossil remains of Lemmus occur abundantly in the later 

 Pleistocene deposits of the British Isles and Western Europe; 

 but the material is fragmentary and after a close study of it 

 extending over many years I am not prepared to determine 

 any of these fossils specifically. 



1. Lemmus lemmus Linnaeus. 

 1758. Mus lemmus Linnjeus, Syst. Nat., 10th ed., 1, p. 59. 

 1777. Glis lemmus Erxleben, Syst. Reg. Anim., 1, p. 371. 



