MIMOMYS 375 



M. savini; JHg ^'^^ '"3 '^'"^ "^ normal form, although the inner and 

 outer triangles of the former tooth are more nearly opposed and 

 less alternating than is usual in any of the species occurring at 

 West Runton. 



Measurements (according to Mehely). — Upper tooth-row 5-3- 

 5-7 mm. {m^ 2-1-2-3; ni^ 1-7-1-8; m" 1-5-1-6). Lower tooth-row 

 5-3-5-6 juv., 5-5-6-1 ad. {m^ 2-5-2-8 ; m.^ 1-5-1-8; m.^ 1-3-1-5). 



In two lower jaws from the same deposit the teeth are larger 

 ()H^ measuring 3 and 3-1, h^ 1'9 and 2 mm.) although precisely 

 like those of M. pusillus in form. 



Remarks. — This species, known only to me by Mehely's descrip- 

 tion and admirable figures, seems to be most closely related to 

 M. intermedius and M. savini of the " Upper Freshwater Bed " 

 (Cromerian). In my opinion its palatal structure, more reduced 

 m^, and smaller size indicate a greater degree of specialization 

 than that attained by any of the species so far discovered in the 

 British Forest-Bed series. 



In the synonymy of M. pusillus Mehely cites with doubt the 

 tooth figured by Newton (Vert. Forest-Bed, PI. xiii, fig. 8), who 

 erroneously stated it to be from West Runton, although it 

 came from the Weybourne Crag of Trimingham. Mehely, how- 

 ever, suspects it to be referable to his M. petenyii, an opinion 

 which I have confirmed above (see under M. reidi). Mehely also 

 refers the subject of Forsyth Major's fig. 22 to M. pusillus, but a 

 study of that specimen, and much other material from West 

 Runton, shows it to belong to another species, M. savini. 



6. t Mimomys newtoni Forsyth Major. 



1902. Mimomys newtoni Forsyth Major, P.Z.S., 1902, 1, p. 103, text- 

 fig. 13, fig. 7; text-fig. 14, fig. 10; Hinton, Proc. Geol. Assoc, 

 21, 1910, p. 491. 



1910. Microtns {Mimotnys) intermedius Newton, Bull. Soc. Beige 

 Geol., Free. Verb., 24, p. 232. 



1914. Microtomijs newtoni Mehely, Ann. Mus. Nat. Hungar., 12, p. 223. 



Ty/je.— B.M., No. M. 6967a; Savin Collection; a left m^, 

 with the cement spaces closed below. 



Type horizon and locality. — Cromerian (Forest Bed or Wey- 

 bourne Crag) of East Runton, Norfolk. 



Range in, time and space. — Late Pliocene. In Britain known 

 from Norfolk, where its remains have been found in deposits 

 ranging in age between the Norwich Crag and the Lower Fresh- 

 water Bed (Cromerian). In Belgium it has been found in the 

 Late Pliocene of Tegelen-sur-Meuse ; in Hungary in deposits 

 of similar age at Beremend and Nagy-Harsany. 



Characters. — Size small, about as in Mlcrotus arvalls ; length 

 of lower molar series about 5 '5 mm., not exceeding 6 mm. 

 Cheek-teeth provided with two roots each in adults ; re-entrant 

 folds parti}' filled with cement. Enamel pattern of m^, vi^, m^ and 

 m^ normal ; m^ with three outer and three inner salient angles, its 



