MUBID^— ARVICOLIN^— ARVICOLA AD8TERD8. 



213 



usual. The skull is perhaps " remurkable for its elongation " ; but it fulls 

 sliort of the specimen of hai/deni, wliich measures 1.14, ami only exceeds 

 average austerus by 0.06. The suppose*! difference in the lengths of the 

 nasals and the nasal branches of intermaxillary, owing to the shortness and 

 truncation of the former, is no distinction, as we find it precisely matched in 

 examples of unquestionable austerus (No. %V-; No. l^). The alleged 

 differences in dentition are simply a little less deep infolding of the enamel 

 loops on the back upper and front lower molars ; so tliat the lateral triangles 

 of the first-named tooth, instead of being closed up along the middle line of 

 the tooth, intercommunicate; and the same is the case with the anterior 

 exterior triangle of the last-named tooth. But this is merely a slight differ- 

 ence in degree, not of kind. Among our specimens are some as closely 

 approaching this pattern as others recede from it; and the differences in this 

 respect among unquestionable austerus are quite as great as between austerus 



. \- 



The following table gives the measurements of our series. 



Tablk LIV.— ifauiimimf* offift^-lwo fjnciment 0/ Arvicola (Pedomys) austerus. 



-Si 



