new Euiupean Volts. 201 



Microtus agrestis exsul, subsp. n. 



Ti/pe.—Aduh female (skin and skull). B.M. no. 6. 3. 1. 3. 

 Collected on North Uist, Hebrides, February 5, 1906, by 

 J. F. Davison, Esq. Presented by the collector. 



Characters. — In general like the huge Scandinavian 

 Microtus a<)r(stis agrestis, but underparts with more evident 

 brownish wash, often becoming a clear rather light ochra- 

 ceous-bufF; first upper molar with small third inner triangle 

 usually present (in 10 among 14 specimens) and almost as 

 well developed as second inner triangle of middle molar. 



Measurements. — Type. Head and body 123 mm.; tail 44 ; 

 hind foot 19; ear from meatus 12, Skull: condylo-basal 

 length 2'6', zygomatic breadth 15'8; interorbital constriction 

 3*2; occipital breadth 12; occij)ital depth 'o'(> ; nasal 8"0; 

 diastema 8'2 ; mandible 18 ; maxillary tooth-row 7*0 ; mandi- 

 bular tooth-row 7*0. 



Specinuns examined. — Fouiteen, eleven from North Uist 

 and three from South Uist, Hebrides * : all but three lent by 

 (Mr. Kinnear. An immature male from Kildalton, Islay 

 No. 392, Kinnear collection), appears to represent the same 

 form, but is too young to be positively identified. 



liemarks. — A supplemental triangle in the first upper 

 molar, similar to that usually ])resent in Microtus agrestis 

 exsul, occurs in 4 among 32 specimens of true agrestis and in 

 only 2 among 48 British mainland skulls. 'J'he cranial 

 characters of fully adult individuals of the Hebridean vole as 

 compared with true agrestis and the common Britisli form 

 are well indicated by the following table (in mm.) : — 



Number Condylo- Upper Lower 



of skulls, basal length. Mandible. tooth-row. tooth-row. 



agrestis .. 9 264 to 28-4 IGGtolS GG to 70 6-2 to 6-6 



exsul 7 27 to 28 17 to 18 G-8 to 70 6-4 to 7-0 



13 25 to 26 lo-4 to 16-2 5-8 to 6-4 5-8 to 6-2 



The discovery of this vole is of unusual interest, as the 

 ])robable existence of some such animal in North Britain 

 was pointed out several months ago f, at a time when the 

 characters of the Hebridean form were unknown. 



* Mr. Kinnear has called my attention to the fact that no voles have 

 yet been found on the island of Lewis, the largest of the Outer Hebrides, 

 t Stejneger, Smithsonian Miscell. Coll. xlviii. p. 478 (May 4, 1907). 



