LOCALLY EXTINCT VOLES 469 



Wellikii-Ustjug, north central Russia) is a large, long-skulled 

 mouse with relatively heavy teeth (condylo-basal length of skull 

 to 30 mm., the condylo-basal length about twice the zygomatic 

 breadth; hind foot 19 to 21); m^ resembles that of M. 

 anglicus in having only three outer salient angles, but the 

 fourth outer angle is still more reduced and the third outer 

 fold is shallow, so that there are only four closed triangles, the 

 fifth opening more or less widely into the anterior loop (Fig. 75). 

 m? has usually a small fourth outer angle ; and m^ has the third 

 outer angle distinct though small. 



M. ratticeps is found at the present time in northern Eurasia, 

 from Skandinavia (in mountains and lowlands) to some point 

 in Siberia, and south to Holland, northern Germany, and 

 Hungary, although it has not yet been detected in Denmark 

 (Winge, Danmarks Pattedyr, 78). It formerly lived in Britain, 

 first appearing in the Clevedon Cave, Somersetshire (Middle 

 Pleistocene), where it is accompanied only by M. malei and 

 C nivalis. In the "middle terrace" horizons of Crayford and 

 Erith, and Fisherton, its remains are common and associated 

 with those of lemmings and a pouched marmot (Citellus) in 

 addition to those of C. nivalis. It is known also from many 

 later pleistocene deposits, as Ightham, Forest of Dean Cave, 

 Langwith Cave, Derbyshire, and " Dog Holes," Lancashire ; 

 in such horizons its remains are scarce and associated with 

 those of M. anglicus, lemmings, Citellus and Pika, while C. 

 nivalis is absent. The late pleistocene bones appear to be 

 identical with those from individuals living in Holland and 

 Germany. According to Hinton {op. cit., 503), M. ratticeps 

 reached this country with Chionomys from France during the 

 later part of the " middle terrace " stage. 



Microtus malei (Hinton, Proc. Geol. Assoc, xx., 48, 1907, 

 first referred to Chionomys and subsequently to Microtus, Proc. 

 Geol Assoc, xxi., 494) is a "species with (typically) a rather 

 generalised dental pattern such as that which probably character- 

 ised the ancestor of several species like M. ratticeps and C. 

 nivalis" and the specimens from the Clevedon Cave upon 

 which this species was originally based represent only its 

 nivaloid variation. It is only known from the Middle 

 Pleistocene of Britain, occurring in the Clevedon Cave, 



