514 MURIDAZ—APODEMUS 
The mandible is slender, with small but well-developed coronoid 
and long, rather slender, angular processes ; the dental foramen is level 
with the alveoli; the incisor roots produce a small external projection 
at the base of each coronoid process. 
Cheek-teeth are typical of the sy/vaticus group, and have been 
described above under the genus (p. 504, Pl. XXVIII. Fig. 5.) 
Exceptional variation:—Melanism appears to be very rare. 
Millais (Zamm., 197) mentions one “ perfectly black,” shown by Borrer 
to Harting, but the specimen was not forthcoming; a “black and 
white” field mouse, which attracted notice by “producing a chirping 
noise,” is recorded by R. P. Williams (Proc. Dublin Nat. Hzst. Soc.) in 
Nat. Hist. Review, v., 1858, 188. A good many completely or partially 
albinic individuals have been recorded, ¢.¢., (1) one from Highwood, 
Middlesex (Cox, /ze/d, 18th January 1873, 51); (2) a pink-eyed 
nursing female, Great Marlow (Cocks, Zoologist, 1884, 226); (3) pale 
buff, Broxton, Cheshire, in Grosvenor Museum, Chester (Newstead, 
Chest. Soc. Nat. Sct. and Lit. Proc., iv., 249); (4) (Forrest, Zoologzst, 
I9I0, 307); (5) three cream-coloured in J. Whitaker’s collection; (6) 
“young albino,” Montgomeryshire (Forrest, J7S.); (7) a buff female, 
black hairs entirely absent, from Brent Knoll, Somerset (No. 3.12.17.1 
of British Museum collection, Percival); (8) male, silvery grey without 
reddish tints, alive with Laver (“7¢, 22nd October 1905). Such cases 
cannot, however, be said to be common; Laver (/¢, 9th April 1904) 
said that he had only seen one, out of a thousand examined. Adams 
says :—“ The only albinism I record is at the tip of the tail (twice).” 
Geographical variation:—In addition to the typical form, four 
distinct sub-species are now recognised in Europe. These are :—(1) 
A. s. bute’, Hinton, from the island of Bute, Scotland, described below ; 
(2) A.s. callipides, Cabrera (Bol. Real. Soc. Espan. Hest. Nat., Madrid, vii., 
227, November 1907), a large dark-coloured form, in which the hind foot 
frequently measures 23 mm., while the condylo-basal length is 23-6 mm. 
or more, inhabiting the mountains of the Pyrenees-Asturias chain, 
and ranging southwards into Portugal; (3) A. s. dtichrurus, Rafinesque 
(Précis des Découvertes Somiologiques, 1814, 13), which agrees with 
callipides in size, but differs from both it and true sy/vatecus in its 
pallid and dull coloration, due to the suppression of the rufous and the 
predominance of the yellow and grey tints; this mouse was described 
from Sicily, and it inhabits the Mediterranean region from the Balkan 
Peninsula to central and southern Spain; (4) 4d. s. creticus, Miller 
(Ann. and Mag. Nat. Hist, November 1910, 460), a mouse no larger 
than true sy/vatécus, but of pale and more yellowish colour, which is 
known only from the island of Crete. A considerable number of 
sub-species have been described from Asia; of these the more con- 
spicuous are:—A. s. ¢auricus, Barrett-Hamilton (Proc. Zool. Soc., 1900, 
