1881.] Himalayas, Tibet, and Afghanistan. 95 



of the angles on opposite sides of the molars corresponding and the 

 spaces on the crowns of the teeth being consequently double or diamond- 

 shaped instead of triangular, and their number necessarily smaller. The 

 number of internal and external angles in the first and second upper molars 

 is however, the same as in A. siJcimensis, and the species may therefore, 

 for the present, be assigned to the same section. 



The Western-Asiatic form above referred to as resembling Neodon in 

 its dentition is A. guentheri, Danford and Alston*, from Asia Minor. 

 The posterior inner angles on the first and second upper molars, judging 

 from the figure given, are less developed than in A. sikimensis (but still 

 they exist), and all the molar teeth, both in the upper and lower jaws, are 

 very similar to those in the Sikkim species. Externally A. guentheri is 

 very different, as it has but a rudimentary thumb without any claw, a 

 much shorter tail, different coloration, &c. 



The following table will show how the species of Himalayan and 

 Tibetan Voles hitherto described may be distinguished by the characters 

 of their teeth : — 



I. The anterior upper molar has 3 angles inside and 3 outside ; 



the second 2 inside and 3 outside. The anterior lower 



molar has normally 7 spaces. 



A. The posterior upper molar terminates behind in a narrow 



process, prolonged backwards in the line of the jaw. — 



Alticola. 



a. The posterior upper molar has two strong internal angles 



and four weak outer angles, the two anterior of the 

 latter widely separated from the two posterior. 

 o. The posterior lobe of the last upper molar behind the 

 second inner angle is much less than half the length 



of the tooth 1. A. $toliczkanus, 



&. The posterior lobe of the last upper molar behind the 



second inner angle is half the length of the tooth 2. A. stracheyi. 



b. The posterior upper molar has 2 internal and 3 external 



angles 3. A tvynnei. 



c. The posterior upper molar has 3 angles on each side. 



a. In the anterior lower molar the first inner angle is 



behind (proximal to) the first outer 4. A. roylei. 



)8. In the anterior lower molar the first inner angle is in 



front of (distal to) the first outer 5. A. blanfordi. 



B. The posterior upper molar does not terminate behind in a 

 narrow process prolonged backward in the line of the 

 jaw. — Paltjdicola. 



a. The posterior upper molar has 3 external angles, and the 



first lower molar 4 6. A. blythi 



b. The posterior upper molar has 4 external angles, and the 



first lower molar 5 .• 7. A. mandarinut ? 



* P. Z. S. 1880, p. 62, pi. v. 



