form was unknown in Shetland I thought that it would prove to be a new subspecies
; but on examining additional specimens I came to the conclusion that this
northern race, although undoubtedly large, especially about the head and ears, had
not sufficient characteristics of its own to warrant sub-specific rank. The figure
of this animal next to those of English M. s. intermedins as drawn by Mr. G.
Lodge in the photogravure plate will at once show such differences as exist.
s o b -s p e c i e s 1 1
T h e I r i s h W o o d M o u s e
Mus sylvaticus celticus, G . E . H . B arre tt-Ham ilto n.
Characters.—Smaller than the typical sylvaticus, this sub-species is characterised
by the darkness of the upper parts, due to a large number of blackish hairs on the
dorsal region. The under side is white. Captain Barrett-Hamilton says that ‘ the
dimensions of ear and hind foot seem to show that these are slightly larger in
proportion to the general body-size than is the case with Irish examples of
M . s. intermedins.'
The general measurements are very similar to those of the common British
Wood Mouse; the length of skull is the same.
D istribution.—Southern and Western Ireland, the Hebrides and Skye, are
given as the home of this sub-species. I obtained a male which appears to belong
to this form at the north end of North Maven, Shetlands, in August 1901
(figured). It is also believed to exist in Portugal. So long ago as 1841 the
Rev. Leonard Jenyns (Blomefield) received Wood Mice from county Kerry and
noticed 1 that they differed considerably from the typical form, being smaller and
darker. In closing his remarks2 on this sub-species Captain Barret-Hamilton says:
‘ A remarkable fact is the occurrence of this mouse on the same island (Lewis) as
the very distinct M. s. hebridensis, which is one of the larger forms of Field Mice.
I am informed by Mr. de Winton that the latter keeps to its own part of the
island, and that probably the two do not intermingle. It is curious that while a
big and a little form of Mus sylvaticus occur here side by side, each finds a
different method of fitting itself for the damp, dull climate of the west.’ I am
not at all sure, however, that these two forms do not intermingle.
1 Ann. and Mag. Nat. Hist. 1841, vol. vii. p. 268. * Proc. Zool. Soc. 1900, p. 403.
VOL. II. B B