698 



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

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

 molar. In both arvalis and orcadcnsis this loop 

 is deeply indented by two re-entrant angles, 

 one on each side, the two angles approximately 

 equal in depth. In M. sandayensis sandnijensis 

 the inner angle remains as in the related 

 species, but the oiiter, 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 difterent from the ordinary type 

 to permit of certain identification of the animal 

 by this character alone. 



Measurements. — External measurements of 

 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). 



J. G. Millais (c & p). 5. 11. 22. 3. 



{Type of species.) 

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

 W. R. Ogilvie - Grant 11,11.2.1-8. 

 (c & p). 



Fig. 139. 



Microtvs sandayensis 

 sandayensis. X 5. 



9. Sanday Island, Orkneys. 



2 9. 

 4(J49 



Sanday. 

 Sanday. 



MiCROTUS SANDAYENSIS WESTR^ Miller. 



1908. Microtus sandayensis ivestrx Miller, Ann. and Mag. Nat. Hist., 



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

 1910. Microtus sandayensis westrx Trouessart, Faune ]\Iamm. d'Europe, 



p. 178. 



Tyjje locality. — Westray Island, North Orkney Islands. 



Geographical distribution. — At present known from Westray 

 Island only. 



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

 angle occasionally as deep as in 31. orcadcnsis ; colour not so pale 

 as in the Sanday vole, the underparts strongly washed with 

 yellowish brown. 



Colour. — General eftect 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-bufi', nearly as in M. orcadcnsis, 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. 



