SYNAPTOMYS 173 



mixed with blackisli hair-tips ; under parts leaden-grey. Rufous 

 mark under each ear. A white patch over each hip. Tail 

 round, well clothed with short stiff hairs which completely 

 conceal the scales; clove-brown above, greyish-white beneath. 

 Paws clove-brown above. 



Skull known from fragments only. Each upper incisor with 

 a broad, but quite shallow sulcus upon its outer face, and with 

 a much nai'rower notch-like groove upon its hinder surface. 

 Cheek-teeth : vt.^ with large jjosterior loop ; outer fold of ni^ 

 moderately deep, leaving the outer and inner portions of the 

 middle transverse loop about half confluent (Fig. 73, 3). 



For external and cranial measurements of type, see tables at 

 end of volume. 



Remarks. — What is left of the skull of the type shows that 

 it was a perfectly adult individual with the temporal ridges 

 completely fused in the interorbital region. 



Notwithstanding Richardson's remarkably full and good 

 description and his statement that this animal might be regarded 

 as intermediate between the lemmings and the voles, it was 

 not until Osgood's paper of 1907 that " Arvicola " horealis was 

 identified as a member of the present genus. A subadult male 

 from Fort Halkett (B.M., No. 63.1.6.12 in al., presented by 

 B. R. Ross) may be referred to 8. horealis, agreeing with the 

 type in general character, in the small size of the hind-foot 

 (15"6), and in the pattern of the molars; the outer fold of m^, 

 however, is deeper, nearly closing off an outer triangle, but I 

 am not inclined to attach much importance to this character. 



Synaptomys hullatus described from Fort Rae, Great Slave 

 Lake, a locality some considerable distance to the south-east of 

 the type locality of *S'. horealis, is treated by Miller (" Lists," 

 1912 and 1924) as a synonym of the present species; but since 

 the hind-foot is considerably larger (18 mm.) and the colour, 

 judging from Preble's description, is somewhat different, it may 

 be a distinct form. 



It is quite likely that, as Hollister (Canadian Alpine Journal, 

 Special Number, pp. 19-20, Feb. 17, 1913) has suggested, ail 

 the forms inhabiting north-western North America will eventually 

 have to be regarded merely as more or less well-marked subspecies 

 of S. horealis. 



5. Synaptomys (Mictomys) dalli Merriam. 



1896. Synaptomys (Mictomys) dalli Merriam, Proc. Biol. Soc. Wash- 

 ington, 10, p. 62. 



Type. — U.S. National Museum; skeleton. 

 Type locality. — Nulato, Alaska. 



Characters. — Generally resembling S. wraugeli, but with 

 larger auditorv bullae and less reduced cheek-teeth. 

 I Colour (according to Osgood, N. Am. F., No. 19, p. 37, 1900) : 



