358 MICROTIN^ 



Type locality and ^on'zon.— Upper Pliocene lacustrine deposits 

 of the Val d'Arno. 



Range in time and space. — This species occurs in the Upper 

 Pliocene of Britain, Holland, Belgium, Italy and Hungary. 



In Britain it is known from the Norwich Crag in Norfolk 

 and Suffolk, from " clay-pebbles " in a " clay-gravel " at East 

 Runton, Norfolk (see p. 376), and from a " shelly crag " (Lower 

 Cromerian or Weybourne Crag) at East Runton. 



In the Norwich Crag it occurs alone, or perhaps in association 

 with M. newtoni; in the "shelly crag" at East Runton it is 

 associated with M. savini, M. intermedins and M. majori. 



In Holland teeth of Mimomys were obtained from a boring 

 at Gorkum; these were referred by Harting (Ver. Comm. Geol. 

 Kaart van Nederland, 1853, p. 103) to " Hypudceus terrestris." 

 Rutten (Die diluviale Saugethiere der Niederland, 1910, p. 88) 

 has described and figured three of these teeth, correctly referring 

 them to the present genus. Of these a fragment of maxilla 

 with the left m^, obtained from a depth of 165-5 metres, is in 

 my opinion undoubtedly referable to the present species, the 

 tooth showing the characteristic islet developed in connection 

 ■with the reduction of its second inner valley. A left m^ and a 

 right m^ from a higher level (127-3-129-9 metres) may also belong 

 to this species or rather to a later development of the same 

 stock; these two specimens Rutten compares with M. inter- 

 medins, but from the general form of the Wj I think its affinities 

 are with M. pUocoenicus. Further study of this specimen and a 

 good figure of its external surface are necessary before it can be 

 satisfactorily determined. A fourth specimen from the same 

 level is referred by Riitten " mit ziemlicher Sicherheit " to 

 Arvicola amphihius ; but such a determination is, in my opinion, 

 open to the gravest suspicion. 



In Belgium the species is known from the Upper Pliocene 

 clay of Tegelen-sur-Meuse, from which deposit a very character- 

 istic left wij has been described and beautifully figured by Newton 

 (Bull. Soc. Beige Geol., 21, 1907, p. 592). 



In Italy, in addition to the jaw from the Upper Pliocene 

 lacustrine deposits of the Val d'Arno upon which Forsyth Major 

 based the present species, two jaws have been obtained and 

 described by Tuccimei (Mem. Pont. Accad. Nuovi Lincei, 9, 

 1897, p. 35) from the Upper Pliocene lacustrine marl of Bocchig- 

 nano in Sabino. From the figures and description these specimens 

 would appear to be referable to M. pliocwnicns or a near ally. 

 Tuccimei has, however, completely misunderstood the characters 

 of the dentition. He states correctly that the molars of Arvicola 

 are rootless ; shows the rooted character of the fossil teeth most 

 clearly in his figures; describes how the cement spaces die out 

 below ; and then says there is no doubt that these remains are 

 to be referred to Arvicola amphihius. The characteristic enamel 

 " islet " is present in the j/ij of the younger jaw, and this 



