708 



MICROTUS RATTICEPS Keyserling and Blasius. 



184] . Arvicola ratticeps Keyserling and Blasius, Mem. presentes a l'Acad. 

 Imp. des Sci. Nat. de St. Petersbourg, iv, livr. 3, p. 333, 1841 

 (date on title-page of completed volume, 1845). (Welikii-Ustjug, 

 north-central Russia.) 



1841. Arvicola arenicola de Seiys-Longchamps, Bull, de l'Acad. Royale 

 des Sci. des Arts et Belles-Lettres de Bruxelles, vni, pt. 2, p. 236 

 (Lisse, near Leiden, Holland. See Jentink, Notes from the 

 Leiden Museum, xxix, p. 263, February 29, 1908). 



1844. Arvicola medius Nilsson, Ofversigt af Kongl. Vetenskaps-Akademiens 

 Forhandlingar, Stockholm, i, p. 34, March 20, 1844 (Lapland, and 

 the mountains about the Gudbrandsdal, Norway). 



1857. Arvicola ratticeps Blasius, Saugethiere Deutschlands, p. 365. 



1887. Microtus ratticeps Lataste, Ann. Mus. Civ. Stor. Nat. Genova, 

 2nd ser., iv, p. 265, January, 1887. 



1899. Ari>[icola] (Microtus) ratticeps var. stimmingi Nehring, Sitz.-Ber. 

 Gesellsch. Naturforsch. Freunde, Berlin, p. 58 (near Brandenburg, 

 Germany). See Bbrig, Arbeiten aus der Kais. Biol. Anstalt fur 

 Land- und Forstwirtschaft, vn, p. 471, 1909. 



1910. Microtus ratticeps, M. ratticeps stimmingi, and M. arenicola Troues- 

 sart, Faune Mamm. d'Europe, p. 179. 



Type locality. — Welikii-Ustjug, on the Dwina River, north- 

 central Russia. 



Geographical distribution. — Northern portions of continental 

 Europe and Asia from northern Russia and the mountains of 

 Scandinavia eastward into Siberia, south to Holland,* northern 

 Germany and northern Hungary. 



Diagnosis.— Size large (hind foot, 19-21 mm.; condylobasal 

 length of skull in largest individuals, 30 mm.) ; second upper 

 molar without postero-internal triangle ; first lower molar with 

 only three re-entrant angles on outer side ; skull long and slender 

 (ratio of zygomatic breadth to condylobasal length about 50), the 

 intertemporal region developing moderate ridge with age ; length 

 of brain-case measured from interorbital constriction to condyle 

 greater than zygomatic breadth. 



External characters. — Essentially as in Microtus agrestis, but 

 thumb usually with somewhat better developed nail, and sole 

 with sixth tubercle relatively smaller. 



Colour. — In general the colour is not essentially different 

 from that of Microtus agrestis, though it shows a tendency to be 

 somewhat darker. Upper parts a coarse mixture of wood-brown 

 and black, the sides occasionally with a slight tinge of russet. 

 Underparts abruptly-defined pale grey tinged with cream-buff 

 and frequently darkened by slaty under-colour. Feet light 

 drab or dull whitish. Tail rather sharply bicolor, dark brown 

 above, whitish below. In a skin from Western Hungary 

 (B.M. 94. 3. 1. 64) there is a noticeable dark dorsal area extend- 

 ing from forehead to base of tail, rather sharply denned clear 



* Not known to occur in Denmark (see Winge, Danmarks Fauna, 

 Pattodyr, p. 78, 1908). 



