698 RODENTIA 



Teeth. — The teeth resemble those of 31. arvalk and M. orca- 



densis except in the form of the anterior loop of the first lower 



molar. In both arvalis and orcadensis this loop 



is deeply indented by two re-entrant angles, 



one on each side, the two angles approximately 



equal in depth. In M. .HandayeriHis sandayensis 



the inner angle remains as in the related 



species, but the outer, more posterior angle is 



much more shallow than the inner. In some 



specimens it is scarcely indicated, while in all 



of the twelve skulls that I have examined it 



is sufficiently different from the ordinary type 



to j^ermit of certain identification of the animal 



by this character alone. 



iiG. 139. Measurements. — External measurements of 



^ smidaycnsis.'^^''Tl\'' type (immature male measured on dried skin) : 



head and body, 86 ; tail, 19 ; hind foot, 17-4. 



Adult male and two adult females from the type locality : head 



and body, 117, 110 and 111; tail, 37-5, 38-5 and 35; hind 



foot, 19, 18 and 18; ear from meatus, 11, 10*5 and 11. 



For cranial measurements see Table opposite. 



Specimens examined. — Twenty, all from Sanday Island, North Orkneys 

 (B.M., U.S.N.M. and Edinburgh). 



9. Sanday Island, Orkneys. J. G. ]Millais (c & p). 5. 11. 22. 3. 



{Type of species.) 

 2 J. Sandav. N. B. Kinnear (c & p). 6. 11. 18. 7-8. 



4d4?. Sanday. W. R. Ogilvie - Grant 11.11.2.1-8. 



(c & p). 



MiCROTUS SANDAYEN'SIS WESTR.E Miller. 



1908. Microtus sandayensis tvestr.-v Miller, Ann. and Mag. Nat. Hist., 



8th ser., i, p. 199, February, 1908. 

 1910. Microtus sandayensis wcstnt- Trouessart, Faune I\Iamm. d'Europe, 



p. 178. 



Type locality. — Westray Island, North Orkney Islands. 



Geographical distribution. — At present known from Westray 

 Island only. 



Diarjnosis. — First lower molar with anterior outer re-entrant 

 angle occasionally as deep as in M. orcadensis ; colour not so pale 

 as in the Sanday vole, the under parts strongly washed with 

 yellowish brown. 



Colour. — General effect above a dark hair-brown approaching 

 bister, the arrangement of colour as in sandayensis, but light tips 

 to hairs of underfur more nearly a dull ochraceous-buff, and dark 

 shading from longer hairs more noticeable. Underparts light 

 ochraceous-buft', nearly as in M. orcadensis, but colour not so rich 

 and clouding from slaty bases of hairs more evident. Feet and 

 tail as in sandayensis, but sprinkling of dark hairs on upper 

 surface of tail more conspicuous. 



