I.ale Pleistocene Voles and Lemmings. 37 



Measxirements. — Type skull : cond)!o-basal leiit^tb 26*9 mm. ; 

 ayf^oinaiic hieailtli 14*0; intemrbiial coiistiictiou 2*7; occi- 

 pital breadth 11*9 ; occipital depth (median) 64 ; nasal 7*1; 

 dinstenic 8*7 ; molar series (alveolus) 64. 



Specimens e^nnined. — Two nearly j)i'rlect and a very large 

 series of imperfect skulls from tht; I^htham Fissures and 

 numerous specimens from other Late Pleistocene deposits. 



liemarks. — This species has long been known to palreon- 

 tolcigists as a conspicuous element in the Late Pleistocene 

 fauna of Western Europe, and they have hitherto followed 

 the lead of Nehrin<r in referring it to J/. fjre(jnlis of Pallas. 

 The skull-measurements given by Pallas show that wjiatever 

 the impel fectly known M. gregalis may be it certainly has 

 little to do with the fossil animal. The zvgomatic and 

 occipital breadths, w hen compared with the skull-length taken 

 as 100, amount to 4.r5 and 3G'4 respectively in M. gre/jali'i, 

 and to 520 and 442 in M. anglicu'<. Among the living 

 species of "' Stenocranius" of which I have seen skulls or 

 descriptions M. (ianshnnicus, Biichner, appears to make the 

 nearest approach to M. anglictts in skull and dentition ; it 

 differs principally in the narrower palate, narrower and 

 shorter rostrum, and lighter zygomatic arches. 



Dicrostonyx henseli^ sp. n., foss. 



Tyyte. — A perfect adult skull in the collection of Mr. Lewis 

 Abbott from the Ightham Fissures. 



Characters. — Size small. Skull: dorsal outline gently 

 convex; combined nasal width little more than a third of 

 nasal length; zygomatic arches flaring more than in D. tor- 

 quntus (Discovery Bay) ; palate teebly sculptured with com- 

 plete postero-lateral bridges ; auditory bullaj very small, 

 egg-shaj)ed, and not inflated anteriorly; presphenoid reduced 

 to a slender rod ; molars heavy. 



Dentition : in the anterior upper molar the fourth or 

 postero-internal prism is reduced, its hinder wall has lost its 

 primitive curvature and passes into the posterior wall of the 

 small fourth outer triangle without forming any minute 

 postero-internal accessory {i. e. vestigial) angulation ; in the 

 second upper cheek-tooth the third inner primn is similarly 

 reduced ; antero-external triangle of last lower molar mucti 

 smaller than second one, and passes in front into the anterior 

 wall of the tootii without forming any minute antero-external 

 vestigial angulation. 



Measurements. — Type skull: condylo-basal length 28"6ram.; 

 zygomatic breadth 19"8; interorbital constriction 4*0; occi- 



