﻿48 



NORTH AMERICAN FAUNA. 



[No. 12. 



Geographic distribution of subgenus. — Microtus cliinensis is the only 

 knowu species of the subgenus. 

 Essential characters : 



Palate aljDormal. 



m 3 Avitliont closed triangles. 



m 1 with triangles mostly open, and Trith 9 salient angles, 



m 3 with triangles mostly open, and with 9 salient angles. 



Mamm;v. 4. 



Plantar tubercles, 6. 



Sole moderately hairy. 



Claws on hind feet longest. 



Fur not specially modified. 



Sl'ull — As remarked hj Mr. Thomas in the original description of 

 Microtus chine)isisj the skull of Anteliomys resembles in a general way 

 that of Evotomys, Unfortunately, I am unable to add any more definite 

 information concerning its characters. 



Bony pala te. — The palate of Anteliomys (PL II, fig. 8) is similar to that 

 of EothenomySj except that the median ridge is produced backward as a 

 distinct spike lying perfectly in the plain of the roof of the mouth. 



Just in front of the strongly developed lateral 

 bridges, the posterior edges of which form the 

 back rim of the bony palate, lie two pits, in 

 which terminate the lateral grooves. These 

 pits communicate freel}^ over (dorsad to) the 

 Fig. 23.— Enamel pattern of nio- lateral brldgcs with the anterior end of the 



lar teeth, mcrotus iAnteli- ^ ^ mCSOpterVgoid foSSa. 



omys) cJunensis. {x5.) J- - =5 



Enamel pattern in general. — The enamel pat- 

 tern in Anteliomys (fig. 23) is characterized by rounded angles, imj)er- 

 fectly closed triangles, and great complexitj^ in the prisms of the back 

 upper molar. 



Front lower molar. — The anterior lower molar is made up of four 

 transverse, perfectly isolated loops. The anterior loop is much the 

 largest and contains three salient angles (two on the inner side). Each 

 of the succeeding looi)S has two salient angles. The tooth thus con- 

 tains exactly the same elements as the corres])onding one in Jlicrotus, 

 the difference in form being due to the fact that in Anteliomys the 

 prisms are ijlaced opposite each other instead of alternately. The 

 prisms on the opposite sides of the tooth are nearly equal in size, 

 thus producing the bilaterally^ symmetrical aiDpearance found to a less 

 degree developed in Alticola and Eothenomys. The figures in the 

 original description of Microtus chinensis'^ give a very poor idea of the 

 teeth. 



Baclz upper molar. — The posterior maxillary tooth is like that of true 

 Microtus except that the posterior loop is greatly lengthened and on 

 the lingual side cut by two reentrant angles, of which .the anterior is 



1 Ann. & Mag. Nat. Hist., Ser. Q, Vol. VIII. p. 118, August, 1891. 



