MICROTUS 701 



squarely truncate. In younger specimens (temporal ridges 

 evident, but not joined) the brain-case is broader and the general 

 form more nearly approaches that of M. orcadensis at the same 

 stage, though the zygomata are longer and less abruptly 

 spreading, and the auditory bullae are smaller. 



Teeth. — In all respects except for their slightly smaller size 

 the teeth resemble those of Microtus orcadensis. First lower 

 molar with well developed antero-external re-entrant angle. 



3Ieasurernents. — External measurements of type (adult male) : 

 head and body, 118; tail, 42 ; hind foot, 1 8 • 5 ; ear from 

 meatus, 12. Adult male and female from the type locality:' 

 head and body, 115 and 114-5 ; tail, 44 and 34 ; hind foot, 18 • 4 

 and 17 • 5 j ear from meatus, 9 - 5. For cranial measurements see 

 Table, p. 707. 



Specimens examined. — Fourteen, all from the island of Guernsey. 



Remarks. — Misled by the extreme narrowness of the very 

 aged type skull, I at first supposed this animal to be a member of 

 the agrestis group with aberrant dentition. Further material 

 shows that it is related to the voles of the Orkney Islands and to 

 the extinct Microtus corneri of the British mainland, the three 

 living species and their fossil relative apparently belonging to an 

 older fauna than that now inhabiting Great Britain and the 

 mainland of Europe.* 



4 (5, 1 ?. St. Martins, Guernsey. 0. Thomas (p). 8. 9. 2. 24-28. 

 (B. H. Bunting.) (8. 9. 2. 27. Type of species.) 



MICROTUS CABRERA Thomas. 



1906. Microtus cabrer/e Thomas, Ann. and Mag. Nat. Hist., 7th ser., xvn, 



p. 576, June, 1906. 

 1910. Microtus cabrerai Trouessart, Faune Mamm. d'Europe, p. 181. 



Type locality. — Rascafria, south side of Sierra de Guadarrama, 

 Province of Madrid, Spain. 



Geographical distribution. — Probably throughout the moun- 

 tainous region of central Spain, but at present only known with 

 certainty from the type locality. 



Diagnosis. — A large member of the arvalis group, equal in 

 size to M. orcadensis (hind foot; 22 mm. ; condylobasal length of 

 skull, 27 mm.). Readily distinguishable from all its allies by the 

 strongly convex dorsal profile of the skull, deep, rounded brain- 

 case, slightly tapering nasals and (in young adult skulls at least) 

 the conspicuous longitudinal furrow in interorbital region. 

 Externally the type is peculiar in the unusual length and 

 conspicuousness of the longer hairs above, those of the sides and 

 rump with noticeable pale tips or sub-terminal annulations. 



Colour. — Hairs of upper parts slate-colour at base, those of 



* See Hinton, Ann. and Mag. Nat. Hist., 8th ser., vi, p. 36, July, 1910. 



