Voles from Yunnav. 155 



^vith the posterior loop followed by three substantially 

 closed alternating- triangk\s, which are succeeded by a nioi-e 

 or less widely contluent pair of triangles, the tooth bein^^ 

 terminated by an anterior loop of variable form and com- 

 plexity ; m^ with an anterior transverse loop succeeded by 

 three substantially closed trian<^les, and terminatcMl behind 

 by a })oste)-ior loop of variable form. The other teeth 

 of noruial Microtine form: m-;^ without closed triangles; 

 in} and /;r with or without extra ])ostero-interual angles 

 (cusp ?/). 



External characters nearly as in true Microtus. Fur soft 

 and full, but not so highly modified for subterranean habits 

 as in Pilyinys. Ears moderately long, quite evident above 

 the fur. Sole-pads 6 usually, but in one species reduced 

 to 5. Claws of hands and feet about equal. Mammae 

 2— 2=r8. 



The presence of only three closed triangles in m^^ as in 

 Piti/).ii/s, instead of five as in true Microtus, is perhaps the 

 most significant character of Neodon. This dental difference 

 between the Fiti/mijs-Vike and the Micro tus-Vike voles is of 

 ancient standing, dating at least from the Upper Pliocene 

 (Cromerian Forest Bed) in "Western Europe ; and agree- 

 ment in this respect with Pitymys may, in my opinion, be 

 regarded as good evidence of the closer affinity of Neodon 

 with Pitymys than with the outwardly more similar voles of 

 the genus Microtus, In Europe Pitymys in competition 

 Avith Alicrotus has disappeared from the surface, and has 

 become, in the countries in which it still survives, strictly 

 fossorial. All the recent members of the genus in that 

 continent have therefore acquired external and cranial 

 specializations fitting them for life underground; and they 

 lack all trace of that peculiar specialization of the most 

 anterior portions of the temporal muscles which has led to 

 the constriction of the interorbital region and the develop- 

 ment of an interorbital sagittal crest in such typical voles 

 as Microtus oi^valis and Stenocranius. But in that great 

 refuge for archaic Microtines formed by the highlands of 

 Central and South-eastern Asia, allies of Pitymys^ viz., the 

 members of the present genus, have suffered less from 

 competition, and they have been able to linger to our day as 

 surface-dwellers. They have, therefoi'e, not acquired the 

 fossorial peculiarities of recent Pitymys ; but, on the con- 

 trary, they have independently proceeded very far along a 

 path of cranial and external specialization closely parallel to 

 that pursued by Microtus in similar conditions. 



Five species (including the new one described below) of 



