DICROSTONYX 163 



8. fDicrostonyx henseli Hinton. 



1855. Misothermus torqiiatus HenscI, Zeitschr. deutsch geol. Gesellsch., 

 7, p. 493, taf. XXV, figs. 12 and 13. Not of Pallas, 1779. 



1872. Myodes torquatus Forsyth Major, Atti Soc. Ital. Sci. Nat. Milano, 

 16, p. 123; Newton, Q.J.G.S., 50, 1894, p. 196. 



1910. IHrrostonyx henseli Hinton, Ann. Mag. Nat. Hist., [8], 6, p. 37. 



Type.—BM., No. M.11,803, Geol. Dept. ; Abbott Collection; 

 presented by Sir H. H. Howorth, K.C.I.E., F.R.S. 



Type locality and Horizon. — Ightham, Kent. Late Pleisto- 

 cene; from a deposit filling fissures in the "Kentish Rag." 



Characters. — Size rather small (dental length in adults up to 

 19 mm., condylo-basal length not exceeding 29 mm.). Cheek- 

 teeth relatively broad, but essentially like those of D. hudso)nus 

 in pattern. 



Skull (Fig. 70) in general form most nearly resembling 

 that of D. hudsonius but smaller; its dorsal contour gently con- 

 vex from before backwards, as in D. hudsonius, but with smaller 

 and less expanded nasals, and relatively shorter diastema ; 

 palate feebly sculptured, with complete postero-lateral bridges ; 

 presphenoid reduced to a slender rod, in correlation with the 

 relatively broader and heavier cheek-teeth ; auditory bullae 

 very small, egg-shaped and not inflated anteriorly, their general 

 form much as in D. hudsonius but their position a little different, 

 lying with their long axes more convergent anteriorly and less 

 nearly parallel with the long axis of the skull. 



Cheek-teeth (Figs. 71, 8 ; 72, 7) relatively broad, but essentially 

 like those of D. hudsonius in pattern. In m^ and ?/i- the posterior 

 walls of the hinder inner triangles are reduced, losing their primi- 

 tive concave curvature and tending to lose their thick enamel; 

 a postero-internal vestigial angle never developed ; m^ with a 

 small antero-internal vestigial angle, but no corresponding outer 

 vestige, the third outer triangle more or less reduced. 



Other parts of skeleton not essentially different from those of 

 the hving members of the genus. 



For measurements, see table at end of volume. 



The following is a list of deposits and localities in which 

 remains of D. henseli have been found. In all cases, unless 

 otherwise stated, the material has been determined by the writer. 



A. GREAT BRITAIN. 



Kent. Ightham, near Sevenoaks; fissure deposit. 



A nearly complete skull (the type); an incomplete skull and 

 several mandibular rami. 



British Museum and Museum of Practical Geology {e.v W. J. 

 Lewis Abbott Collection); and in collection of Dr. Frank 

 Comer. 



Middlesex. Lea Valley ; Third Terrace deposits at Bonder's End and 

 Angel Road. 



Abundant remains, including a nearly complete skeleton, and 



