DICROSTONYX 397 



from Quedlinburg, Saxony (Hensel, op. cit. supra, p. 393) ; 

 Eppelsheim, near Darmstadt, Hesse, Germany ; and Hohlen- 

 stein, near Ulm, South Germany (Forsyth Major). 



In England the genus makes its first appearance, with 

 Lemmus, in the brick-earth of Erith, Thames Valley (Newton, 

 Geol. Mag., October 1890, 454), and is present also in later 

 pleistocene deposits. It was extremely abundant, and occurred, 

 as first pointed out by Forsyth Major {op. cit., 123), as two 

 cotemporary species now both extinct, D. gulielmi and D. 

 henseli. 



Of these, D. gulielmi^ was described from specimens in the 

 Taunton Museum, obtained in Wookey Hole Cave, Somerset. 

 It is characterised by large size, short and broad incisive 

 foramina, broad nasals, and heavy teeth, ni^ and m^ having minute 

 postero-internal salient angles. Hinton has identified it from 

 Langwith Cave, Derbyshire [Ann. and Mag. Nat. Hist., July 

 1910, 38 ; Forest of Dean Cave, Gloucestershire ; Crayford 

 and Erith brick-earth ; Kesh caves, Co. Sligo, Ireland (where 

 Dicrostonyx was very numerous in some strata), and from 

 France. 



The other species, Dicrostonyx henseli of Hinton (pp. cit, 

 37), described from a skull in the collection of Abbott, from 

 Ightham Fissures, Kent, has also been identified from the 

 Arctic Bed of Angel Road, Tottenham, Middlesex (Hinton, 

 Quart. Journ. Geol. Soc, June 191 2, 249); Langwith Cave, 

 Derbyshire ; Doneraile Cave, Co. Cork (where Dicrostonyx 

 occurred with Lemmus in enormous numbers, see Ussher, 

 op. cit. supra, p. 394) ; as well as from Quedlinburg (Hensel's 

 original skull of ambiguus, the dental peculiarities of which 

 were noticed by its discoverer). This is a small species 

 with reduced tooth-pattern, n^ and m^ lacking the minute 

 postero-internal salient angles, and having the posterior wall 

 of the postero-external triangle reduced ; it thus resembles 

 rather D. hudsonius of Labrador, but is smaller than that 

 species ; it has also less expanded nasals, the presphenoid bone 

 is reduced to a mere rod, and the teeth are heavier. 



Remains from the following localities have not been assigned 



' Arvicola gulielmi, Sanford, Quart. Journ. Geol. Soc, xxv., 1870, 125, pi. viii., 

 figs. 4 and 4a. 



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