Fig. 72. — Dkrostonyx. 



Crown views of lower molars : — • 



1. Dicrostonyx grcenlandicus. Discovery Bay. Right tn^, rti^, and tn^ 



(B.M., No. 77.8.6.5a). 



2. Dicrostonyx guUelmi Sanford. Pleistocene ; Langwith Cave, Derby- 



sliire. Left m^, wij, and m.^. 



3. Dicrostonyx gulielmi Sanford. Pleistocene; Edenvale Caves, Co, 



Cork. Right Wj, m^, and m^ {Dublin Museum). 



4. Dicrostonyx hudsonius Pallas. Labrador. Left m^, m^, and /n. 



(B.M., No. (51.2.4.1). 



5. Dicrostonyx hudsonius Pallas. 



61.2.4.2). 



6. Dicrostonyx giilielmi Sanford. 



Labrador. Right m^ {B.M., No. 



Pleistocene; Kesh Caves, Co. Sligo, 

 Ireland. Left ?nj (Dublin Museum). 



7. Dicrostonyx hensrli Hinton. Pleistocene; Ightham Fissures, Kent. 



Left m^, m^, and m^. 



8. Dicrostonyx henseli Hinton. Pleistocene; Doneraile Caves, Co. 



Clare, Ireland. Left tn^, m^. and m3 (Dublin Museum). 



9. TJzcro.f/oH ?/.r sp. Pleistocene; England. Right m 3 showing abnormal 



reduction by insulation of the first inner infold. 

 10. Dicrostonyx torquatus ungulatus v. Baer. Novaya Zemlya. Right 

 »«i, 7«2, and r«3 of young individual (B.M ., No. 80.3.29.2). 



