DICROSTONYX ICl 



tooth a more or less well-marked postero-internal vestigial angle ; 

 rwg with its third or antero-external triangle less reduced than in 

 D. henseli and frequently with a more or less well-marked minute 

 fourth outer vestigial angle. 



For measurements, see table at end of volume. 



Remarks. — Sanford's name for this species was revived by me 

 in 1910 after a careful comparison of the fossil material then 

 available with the fine series of recent skulls from Discovery Bay. 

 At that time the Discovery Bay animal was believed to be iden- 

 tical with D. torquatus Pallas, and the comparison left and leaves 

 no room for doubting that it is distinct from I), gulielmi. But 

 further work has shown that the Discovery Bay Lemming is in 

 turn specifically distinct from D. torquatus and has now to bear the 

 name D. grcenlandicus Traill. To judge from the scanty material 

 representing D. torquatus as now understood, the latter species 

 makes a nearer approach to the fossil form ; but the recent 

 material is inadequate to enable us to appreciate the specific 

 characters of D. torquatus. The fossils are larger and have heavier 

 teeth, and in wA and m^ the postero-external triangles are rela- 

 tively large, that of tn^ exceeding that of m^ in size, whereas in 

 recent D. torquatus they are smaller, subequal in size in m^ and m^ 

 or else slightly larger in the former tooth than in the latter. 

 On these grounds, pending the acquisition of further recent 

 material, D. gulielmi may be maintained as a distinct species. It 

 would at present be unwise and misleading to identify the fossils 

 in question with what is in fact the least known of all the recent 

 species. 



The following is a list of the deposits and localities in which 

 remains have been found with short descriptions of the material 

 upon which the records are based. In all cases, unless otherwise 

 .stated, the material has been studied and determined by the 

 writer. 



A. GREAT BRITAIN. 



Somersetshire. Hutlon Cave. 



Five mandibular rami (co-types of the species) and two frag- 

 mentary skulls originally described by Sanford (Q.J.G.S., 26, 

 1870, p. 125, pi. viii, figs. 2 and 4). Re-examined by me (Fig. 

 71, 4 and Plate V). 



Taunton Museum. 



Somersetshire. Aveline's Hole, Burrington C'oombe. 



Lower jaws at first referred doubtfully to D. henseli; but much 

 more extensive material collected later proves the species to be 

 D. gulielmi (Hinton, Proc. Bristol Univ. Spelaeol. Soc, 1, p. 75, 

 1922, and 2, p. 34, 1924). 



Bristol Univ. Spelceological Society's Museum. 



Devonshire. Chudleigh Fissure. 



Two palatal fragments showing between them m^-m^ ; and part 

 of a mandibular ramus. 



A. S. Kennard, F.G.S. 



