Indigenous Icelandic Terrestrial Mammalian Fauna. 447 



understood the sources of information made use of by him. 

 Hence I have thought it desirable to investigate the circum- 

 stances more closely — and this so much the more, as it may 

 certainly be supposed that foreign naturalists will hit upon 

 many of the difficulties which have led Murray astray, or at 

 least upon some of them. 



The animal which possesses this great significance is the 

 Icelandic heath-mouse or wood-mouse, which was regarded 

 by Thienemann as a distinct species, and described and figured 

 by him under the name of Mas islandicus, Th., but which will 

 rather be regarded by other naturalists as a variety of our 

 common wood-mouse (Mus sylvaticus, Linn.*). It is, indeed, 

 the only land mammal which can be regarded with some pro- 

 bability, if not with absolute certainty, as aboriginally belong- 

 ing to the country; for the other land mammals are, first, 

 domestic animals (horses, cows, sheep, goats, pigs, dogs, and 

 cats) introduced with the inhabitants early in the middle ages ; 

 and, in the next place, at various subsequent times two wild 

 animals were introduced, by the interference of man, in order 

 to people the interior of the country — namely, hares and rein- 

 deer ; whilst the rat and the house-mouse have been involun- 

 tarily introduced by commerce. Lastly, icebergs bring white 

 bears to the country, if not every year, at least very frequently ; 

 but it seems to be only quite exceptionally that this animal 

 has remained upon the island throughout the summer. An- 

 other guest which the ice likewise seems to bring frequently 

 is the mountain-fox, the Melrakki of the Icelanders ( Cam's 

 lagopus, Linn.) ; and although this is one of the generally dis- 

 tributed and common animals over the whole country, it must 

 nevertheless also be regarded as introduced only in the above 

 manner. 



It is therefore of importance correctly to understand the na- 

 ture and origin of this mouse, which is found in the open 

 country, pretty far from human habitations. 



Murray thinks that two statements, made by Eg. Olafsen 

 and Henderson, as to the peculiar mode of life of the Icelandic 

 heath- or wood-mouse clearly indicate that this can only be 

 a lemming (Myodes) — most likely M. groznlandicus, Traill, 

 or M. hudsonius, Pall., — and that they can hardly apply by 

 any means to the genus Mus, or at least to our wood-mouse 



* Whether Mus sylvaticus, Linn., is a collective species, and includes 

 several nearly allied forms, is not thoroughly decided, but it is probable. 

 E. Erslev made some remarks upon it, and upon an individual of Thiene- 

 mann's Mus islandicus captured by me in 1839, far from human habi- 

 tations, upon a heath at Rangaaen, at the meeting of Scandinavian 

 naturalists in 1847 (see its ' Fordhandlinger,' pp. 944-945.) 



