546 MURIDA—APODEMUS 
the latter regards it as one of the phases of sylvaticus, which “is a 
polymorphic species.” According to both writers, sylvaticus and 
fiavicollis intergrade; and both may be found mingled in the same 
colony. Still, the broad fact remains, according to Collett, that in 
southern Norway the vast majority of the Field Mice of the coastal 
lowlands are typical sy/vatécus, the vast majority of those dwelling in 
the high mountain pastures are typical flavzcoll7s, while the intermediate 
ground between the two situations is the most usual habitat of the 
intermediate mice. Further, it is a remarkable fact that although 
Britain has been occupied, but perhaps not continuously, by members 
of the sy/vaticus group since the Upper Pliocene (Forest Bed) period, 
and that although their fossil remains have been found in several 
horizons of widely different ages, it is not until the late Pleistocene of 
Ightham that remains of a form (A. /ewzsz, Newton) similar to, if it 
be not identical with, favzcollés are met with. It is also a fact that 
A, flavicollis has not found its way into any of the islands other than 
Britain. The status of A. flavicollis is, as is the case with other Field 
Mice of the sy/vatecus type, undoubtedly a difficult thing to determine; 
but the facts just cited seem to support the opinions of de Winton and 
Miller. Some small proportional differences in certain regions of the 
skull, described below, also support the claims of /f/avzcollzs to specific 
recognition. 
Distribution :—A. flavicollis is distributed throughout Central 
Europe, ranging from at least southern Skandinavia and Finland south- 
wards to the Pyrenees and Alps, and from Britain eastwards to Greece, 
Rumania, and western Russia) How far to the north its range 
extends is unknown. It is represented in the Himalayas by close 
allies, and the range of the group may extend still further eastwards. 
In Norway, according to Collett, dA. flavicollis is the predominant 
Field Mouse of the wooded valleys of the interior and the adjoining 
sub-Alpine tracts; A. sylvaticus, on the other hand, being restricted 
principally to the lowland coastal region. Mice which appear to be 
intermediate in character are met with in the intervening belt of 
country. A. flavicoll’s ascends to the mountain pastures, or a height 
of about 3000 feet. From Fatio’s description of the Swiss Field Mice 
(p. 212) it would appear that favzcoll’s is the prevalent mountain form 
in the Alps; he mentions specimens taken in the Oberland at a height 
of about 1900 m., and others from the Engadine at about 2500 m.; 
from the context it would appear that these were flavicol/?s rather than 
sylvaticus. 
In Britain it is not known to occur further north than Northumber- 
land; the British form is regarded as sub-specifically distinct from the 
typical continental favzcol/zs, 
Distribution in time:—As stated above, no trace of this species 
