424 MURID^— EVOTOMYS 



expanded in front, with their lateral borders slightly but distinctly 

 concave. The rostrum is shallow, as in E, norvegicus, its least depth 

 behind the incisors not exceeding its anterior width. The auditory 

 bullae are about as in norvegicus. m? has a third inner infold and a 

 fourth inner salient angle, the latter usually well developed. 



Skull: — Length, condylo - basal, 24-1 to 25-3; of nasals, 6-8 to 

 7-8; of diastema, 6-3 to 'j-'j; of mandible, 15-1 to 15-7; of maxillary 

 tooth-row, 5-2 to 5-7; of mandibular tooth-row, 5-1 to 5-4; breadth, 

 zygomatic, 13-5 to 14-5; inter-orbital, 3-8 to 4-1 ; occipital, 11-4 to 121 ; 

 depth, median occipital, 6-o to 6-6. 



Status : — Alston's Bank Mouse is, like E. skoinerensis, probably a 

 relict of an ancestral form of large size which occupied Britain before 

 the arrival of glareolus. Being allied to E. nageri norvegicus of 

 Skandinavia, it is the latest link in the chain connecting the mammals 

 of Scotland and Skandinavia, and its existence is apparently another 

 indication of a comparatively recent land-connection between the two 

 countries. 



THE RAASAY BANK MOUSE. 



EVOTOMYS ERICA, Barrett-Hamilton and Hinton. 



1913. EvoTOMYS ERICA, G. E. H. Barrett-Hamilton and M. A. C. Hinton, Ann. 

 and Mag. Nat. Hist., October 1913, 361 : described from Raasay, near Skye, 

 Scotland ; type specimen. No. 14.1.30.5 of British Museum collection. 



Distribution and History: — This mouse was discovered on the 

 island of Raasay in April 19 13 by Montague (see footnote, p. 422 

 supra), who found it rather scarce ; his three specimens were " trapped 

 in big heather." 



Description : — It resembles E. alstoni in general appearance 

 and colour, but is slightly larger, has a more robust tail, and the ventral 

 surface much more heavily washed with buff, in sharp contrast with 

 the dark brown of the flanks and upper surface of the tail. 



The skull is distinguished from that of E. alstoni by its much 

 larger cheek-teeth, broader zygomatic arches, heavier jugals, more 

 salient and extensive post-orbital crests, flatter parietals, narrower 

 inter-pterygoid space, wider pterygoid fossae, vertical instead of 

 ventrally divergent pterygoids, and auditory bullae with their antero- 

 internal parts produced inwards as blunt points instead of being 

 rounded. The mandible differs principally in its larger size, and in 

 having the lower borders of the angular processes widened into broad 

 surfaces for the insertion of the superficial parts of the masseter 

 muscles: the width of these muscular facets is 1-4 mm. as against 

 04 mm. in E. alstoni. 



The teeth are of normal form, differing from those of alstoni 



