514 MURID^— 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 sylvaticus group, and have been 

 described above under the genus (p. 504, PI. XXVIII. Fig. 5.) 



Exceptional variation: — Melanism appears to be very rare. 

 Millais {Mamm., 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. Hist. Soc.) in 

 Nat. Hist Review, v., 1858, 188. A good many completely or partially 

 albinic individuals have been recorded, e.g., (i) one from Highwood, 

 Middlesex (Cox, Field, i8th 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. Sci. and Lit. Proc, iv., 249); (4) (Forrest, Zoologist, 

 1910, 307); (s) three cream-coloured in J. Whitaker's collection; (6) 

 " young albino," Montgomeryshire (Forrest, MS^ ; (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 {lit., 22nd October 1905). Such cases 

 cannot, however, be said to be common ; Laver {lit., 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 : — (i) 

 A. s. butei, Hinton, from the island of Bute, Scotland, described below; 

 (2) A.s. callipides,Ca.hT&vaL. {Bol. Real. Soc. Espan. Hist. 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. dichrurus, Rafinesque 

 {Precis des Dicouvertes Soniiologiques, 18 14, 13), which agrees with 

 callipides in size, but differs from both it and true sylvaticus 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) A. s. creticus. Miller 

 {Ann. and Mag. Nat. Hist., November 1910, 460), a mouse no larger 

 than true sylvaticus, 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. tauricus, Barrett-Hamilton {Proc. Zool. Soc, 1900, 



