ALLEN: AMERICAN COLLARED LEMMINGS. 531 



General characters. — Closely related to ruhricatus from which it 

 differs in its relatively longer and more slender rostrum, its weaker, 

 less broadly rounded zygomata, and slightly more protruding incisors. 

 External characters unknown. 



Measurements. — The type-skull has the following dimensions: — 

 palatal length 18.8 mm.; diastema 10.9; nasals in median line 9.2; 

 zygomatic breadth 21.3; interorbital breadth 4.6; upper molar row 

 (alveoli) 8. 



Geographic distribution. — Confined, so far as known, to the island 

 of Unalaska, Alaska Peninsula. 



Remarks. — This Lemming is still unknown except from skulls. 

 In his original description. Dr. Merriam contrasts its cranial and 

 dental characters with those of the very different hudsonius only, 

 and makes no comparison with the form from the mainland of Alaska, 

 to which it is closely related. The only truly diagnostic character 

 given is that of the rounded zygomata, which in the type-skull and 

 one other younger skull, are apprcc-nbly less heavy and less squarely 

 bowed, as compared with skulls of rubricatus of approximately the 

 same age. The squamosal portion of the arch is noticeably more 

 slender and ^athout the slight angular projection at the posterior 

 edge. In addition, both these skulls have a decidedly longer and 

 more slender rostrum, with somewhat more protruding incisors. In 

 view of these apparent differences, the Unalaska Lemming may be 

 considered distinct for the present. More specimens from the Alaska 

 Peninsula may show complete intergradation since the adjacent 

 islands are not separated by distances greater than a lemming might 

 occasionally traverse. The only lemmings I have seen from the 

 Alaska Peninsula are one from Chignik and one from Muller Bay, 

 both too young be of much value in this connection. Possibly 

 color-differences may be found. 



Since the above was written, I have had for examination twenty- 

 five additional skulls of adult Lemmings lately obtained by the U. S. 

 Biological Survey from Unalaska. All were taken from owl-pellets. 

 This fine series amply bears out the cranial differences previously 

 mentioned as distinguishing this race from typical rubricatus. The 

 longer rostrum, more proclivous incisors, and weaker, more rounded 

 zygomata prove to be uniformly characteristic. 



Of Dr. Merriam's original specimens, there were but four skulls, 

 taken from owl-pellets. None was numbered, and three of them 

 are badly broken, but the fourth has been taken as the actual type 

 and was so labeled later. 



