Vol. 67.] TEETH FROM THE WEALDEN OP HASTINGS. 270 



and that at the rounded end is much the larger — not extending 

 quite to the edge of the tooth, though occupying nearly half the 

 length of the crown. The other two external cusps are almost 

 equal in size, and are followed at the truncated border by a low 

 transverse ridge, which thickens within the last external crescent 

 and passes up nearly to the apex of the largest internal cusp. 

 There is no trace of a cingulum along either the internal or the 

 external border. The roots of the tooth are not exposed. 



Dipriodon valdensis, sp. nov. : crown of molar tooth, upper (A), 

 outer (B), and terminal (C) views, 15 times nat. size. 



[Discovered by M. P. Teilbard de Chardin in the Ashdown Sands, 

 Fail-light Cliffs, Hastings.] 



This very small dental crown evidently belongs to one of the 

 Multituberculata (or Allotheria), but its black shining enamel 

 differs considerably in appearance from the paler coloured and 

 faintly-cracked enamel of the other AVealden teeth which have 

 been provisionally referred to Plagiaulax. It is also distinguished 

 from the molars of the typical species of that genus by the arrange- 

 ment and shape of the coronal cusps. These cusps spread far towards 

 the middle of the tooth, and most of them, if much worn, would 

 exhibit a crescentic shape ; whereas the cusps in a corresponding 

 molar of Plagiaulaw are more closely confined to the raised marginal 

 rim, and would not at any stage of wear expose a crescentic section. 

 The new AYealden tooth must therefore be assigned to one of the 

 so-called ' selenodont' Multituberculata, of which the Lower Jurassic 

 Stereognathus l and the Upper Cretaceous J\/eniscoessus and Selena- 

 codon are typical examples. 2 Some of the teeth of this group bear 

 three, others only two rows of cusps ; and it seems likely that 

 animals with 3-ridged molars in one jaw would have 2-ridged 



1 K. Owen, ' Monograph of the Fossil Mammalia of the Mesozoic Formations r 

 (Palaont. Soc. 1871) p. 18 & pi. i, figs. 27-30. 



2 See especially O. C. Marsh, ' Discovery of Cretaceous Mammalia ' Amer. 

 Journ. Sci. ser. 3, vol. xxxviii (JS89) p. 86 & pi. ii. 



Q. J. G. S. No. 266. u 



