264 MICROTIN^ 



darker and less distinctly bicoloured in immature specimens. 

 In one adult male the white hairs covering the lateral glands 

 form oval patches half an inch in length. 



Skull long and narrow, not thick or angular; rostrum long 

 and decurved. Zygomata smoothly arched. Nasals usually 

 notched, rarely truncate behind, terminating in line with pre- 

 maxillaries. Frontals .slight, concave behind. Palatine bones 

 short; lateral bridges complete before maturity. Incisors large; 

 molar series long. 



For external and cranial measurements, see table at end of 

 volume. 



Remarks. — I have seen no material representing this interesting 

 species. Judging from Mr. Bailey's description quoted above 

 E. ivrangeli would seem to be analogous to the members of the 

 European E. nageri group. 



26. Evotomys dawsoni Merriam. 

 (Synonymy under subspecies.) 



Range. — Yukon, from Finlayson River and Fort Liard west 

 to Yakutat, and northwards along the coast to Norton Sound. 

 Hawkins and Hinchinbrook Islands, Prince William Sound, 

 Alaska. 



Characters. — A robust, short-tailed, bright-coloured species 

 (hind-foot 20 mm. ; basal length of skull 22-5 mm.). Tail 

 rarely twice as long as hind-foot, well haired, but not bristly as in 

 E. rutilus. Ears prominent and well haired. 



Skull large and thick-walled, relatively short, wide and angular, 

 with the smallest and flattest auditory bullae among American 

 species; basioccipital unusually wide between bullae. Nasals 

 terminating behind in line with pre-maxillaries, pointed in imma- 

 ture, rounded in adult skulls, never truncate. Pterygoids strong 

 and prominent, their ends showing in profile below the small 

 flattened bullae. Palatines short, rectangular, with incomplete 

 lateral bridges except in old skulls. Posterior margin of palate 

 with a central notch, deepest in immature specimens. Incisors 

 large, with dark orange enamel. Molar series long and narrow. 



Geographical differentiation. — Two subspecies are at present 

 recognized, viz., E. dawsoni dawsoni of the mainland and E. d. 

 insularis of Hawkins Island. 



Remarks. — This would seem to be the representative of 

 E. rutilus in north-western North America. Bailey (Proc. Biol. 

 See. Washington, 11, p. 122) says : — 



" The combination of large size and short tail, notched palate 

 and small audital bullae, while distinctly separating the species 

 from all others south of its range in America, brings it in closer 

 relationship with E. rutilus. From rutilus, however, it differs 

 in longer, slenderer, less hairy tail, slenderer feet, duller colour, 

 with less rufous on ears, and the following important cranial 



