303 



Explanation of Fio. 91. 



FiQ. 1. A. phasvia. la right upper, 16 left lower molars. (B.M., No. 

 12.4.1.116). 



2. A. slrachcyi. 2a right upper, 2b. left lower molars. (B.M., No. 



6.12.3.19.) 



3. A. (Plahjcranias) slrelzowi. 3a. right upper, 36. left lower molars. 



{B.M., No. 8.11.6.8.) 



4. A. worlhiwjtoni. Left m'. (B.M., No. 12.4.1.190.) 



5. A. worthingtoni. Left m*. (B.M., No. 12.4.1.115.) 



6. A. worthiiujtoni. Left ?»'. (B.M., No. 5.12.4.9.) 



1 . A . worthingtoni. Left m'. (B.M., No. 12.4.1.188.) 



8. A. blanfordi. Left m^. (B.M., No. 1.8.4.10.) 



9. A. roi/lei. Left m^. (B.M., No. 14.7.10.225.) 



10. A. roylei. Left m^. (B.M., No. 14.7.10.222.) 



11. A. royhi. Left m^. (B.M., No. 14.7.10.220.) 



12. A. montosa C' imitator"). Left wj^ (B.M., No. 12.11.26.18.) 



13. A. Uanfordi lahnlius. Left »»». (H. W. W. 2722.) 



14. A. albicauda. Left m^. Skardu (B.M., No. 5.10.8.5.) 



15. -'1. stracheyi. Left m'. (B.M., No. 7.9.6.7.) 



16. ,-1. stracheyi. Left m'. (H. W. W. 2721.) 



17. A. roylei. Right 7n^. (B.M., No. 14.7.10.225.) 



18. A. alhicnuda. Right m^. (B.M., No. 5.10.8.5.) 



19. A. worthingto7ii. Right OTj. (B.M., No. 5.12.4.9.) 



20. A. blanfordi. Right jftj. (B.M., No. 1.8.4.10.) 



the braincase. Auditory bullae well developed, often considerably 

 inflated, invariably simple, thin-walled, and lacking any trace of 

 spongy bone-tissue within. Mandible normal; lower incisor 

 displacing m^ lingually, and ascending into the condylar process 

 to about the level of the alveolar margin of the ramus. 



Cheek-teeth rootless, growing from persistent pulps ; a small 

 quantity of cement present in the re-entrant folds ; enamel more 

 or less well differentiated, as in the higher voles. Enamel pattern 

 of m^, m^, m^, and m^ essentially as in normal voles, and lacking 

 traces of additional vestigial angles behind (m^, ?/r) or in front 

 (ffij, Wig) ; nil (Fig. 91. 16-36, 17-20) with a posterior loop, followed 

 by five alternating and more or less completely closed triangles, 

 and terminated by an anterior loop of variable form, which is more 

 or less confluent posteriorly with the fifth triangle, the tooth 

 showing in most species four outer and five inner salient angles. 

 The last upper molar, m^, varies much in form in different species. 

 When most complex (Fig. 91, m) this tooth has an anterior trans- 

 verse loop, followed by six alternating triangles, of which, however, 

 only the second and third are substantially closed, and is 

 terminated by a short posterior loop. When most reduced 

 (Fig. 91, 15, 16) m^ has an anterior loop, followed by three 

 alternating triangles only, and is terminated by a posterior loop 

 of variable length and form ; sometimes the posterior loop is very 

 long and narrow, forming more than half the length of the entire 

 crown ; sometimes it is short and broad, forming less than half the 

 length of the crown. According to its degree of reduction, the 

 number of salient angles present in he m^ in this genus varies 



