476 SMITHSONIAN MISCELLANEOUS COLLECTIONS [voL. 48 
‘ 
lemmus) which Scharff considered as belonging to the [second] 
Siberian invasion. It is characteristic of the past and present dis- 
tribution of these so-called “ Arctic’’ animals that besides Norway 
they inhabit Great Britain and Ireland, the Alps and the Pyrenees, 
or have been found fossil in these countries and south of these moun- 
tains. Species which at the present day also inhabit extensive areas _ 
in the Arctic regions to the east of Scandinavia may have entered 
this peninsula from the east and north over Finland, in which case 
the Scandinavian species would be of dual origin. Similarly, 
species also living to the south and southeast may have entered 
southern Sweden shortly after the recession of the ice cap and 
spread northward. Thus a triple origin: even is conceivable, as 
members of the same species may have come by all three routes. 
Whether we may be ablé to verify this multiple descent in the 
animals now inhabiting the peninsula, depends in each individual 
case upon the degree of plasticity of the parental form and also 
upon to what extent the members of the various invasions have 
been able to interbreed after meeting again on Scandinavian soil. 
No critical examination of the fauna with this particular object in 
view and based upon sufficient material has ever been attempted. 
There are plenty of hints, however, in the literature of such multiple 
origin of several of the species involved. Thus Nilsson, in his 
Skandinavisk Fauna, Daggdjuren (2 ed., 1847, p. 444) refers to sev- 
eral Swedish forms of Lepus timidus and to the possible distinction 
of the north Russian Lepus variabilis as‘a separate form.’ Barret- 
Hamilton recognizes two Scandinavian forms of squirrel (Sciurus 
vulgaris; Proc. Zool. Soc. London, 1899, p. 6). There are also 
indications that Mus sylvaticus in Scandinavia may be of multiple 
origin,? and similar hints are plentiful with regard to many of the 
’ other micromammalia. 
The scientific record of these is very incomplete as yet, but in a 
* Barrett-Hamilton, Proc. Zool. Soc. London, 1900, pp. 88-91, refers to two 
of Nilsson’s hares as Lepus timidus and Lepus timidus collinus, apparently 
considering the latter equivalent to the supposed larger northern form repre- 
sented by the two large north Russian skulls examined by him. In this I 
think he is mistaken, for Nilsson expressly says that his Lepus borealis, with 
which he synonymizes his earlier L. borealis collinus is a smaller form than 
his L. borealis campestris (= L. canescens). The latter is from southern 
Sweden however. The large north Russian form, possibly extending into 
northern Sweden, should probably stand as Lepus timidus variabilis. See 
also Lilljeborg, Sveriges och Norges Ryggradsdjur, I, Daggd)., 1874, pp. 
420-422. 
* Barrett-Hamilton, Proc. Zool. Soc. London, 1900, p. 405. 
