EVOLUTION OF THE SKULL AND TEETH OF EOCENE TITANOTHERES 



343 



and the same length as in p^ but p^ is relatively much 

 broader, the length of the ectoloph being 21 millimeters 

 and the breadth across the crown 22; the deuterocone 

 is more median in position, elongate, and flattened 

 internally, as in T. ultimum; this tooth also exhibits 

 a low antero-external style. In p'' this style 

 is still more prominent, the protocone and 

 tritocone convexities of the ectoloph are 

 more symmetrical, and the crown seen 

 from above is more quadrangular, the 

 deuterocone being sharp and slightly flat- 

 tened internally. 



Of the inferior premolars pi (preserved 

 in Am. Mus. 1560) is spaced, lying 13 milli- 

 meters behind the canine and 3 millimeters 

 in front of P2; it is laterally compressed 

 (12 by 7 mm.), sharply pointed, and simply 

 plano-convex in section, with a notice- 

 able paraconid, or anterior style. P2 is 

 elongate, laterally compressed, 22 by 10 

 millimeters (in Am. Mus. 1560), with an 

 elevated protocone, rudimentary antero- 

 internal cusp (=metaconid) and well- 

 developed postero-external cusp (=hypo- 

 conid), slightly concave internally. P3 ex- 

 hibits more symmetry; the protoconid still being more 

 elevated than the postero-external cusp (=hypoconid), 

 the proportions of the crown being a shade larger in the 

 type than in Am. Mus. 1560 (ap. 22 mm., tr. 14); the 



analogous to the metaconid; the anterior lobe (=tri- 

 gonid) is much higher, however (15 mm.), than the 

 posterior (12 mm.). 



Molars. — The superior molars (103 mm. in type) 

 exhibit prominent external cingula feebly continuous 



P3 ^ ^p^ 



FiGUHE 291. — Upper and lower teeth of Telmatherium cuUridens, showing 



their mechanical relations 

 One-half natural size. Princeton Mus. 10027 (type). A, Crown view; upper teeth (light line), 



with pattern of lower teeth (heavy line) projected upon them. B, Internal view of the same, 



showing the crushing action of the cones and conids. 



around the styles in m\ m^, and internal cingula 

 nearly continuous on the inner sides of m^, m'. 

 The conules are represented merely by a vestige in 

 m'. The internal cones (protocones and hypocones) 



Figure 292. — Upper and lower teeth of Telmatherium cuUridens, interlocked 



Outer side view. One-half natural size. Princeton Mus. 10027 (type), reversed; upper part of Bridger formation (level C or D), Bridger 

 Basin, Wyo. This view shows the shearing or cutting action of the grinders by the interaction of the superior and inferior crescents 



form is thus feebly molariform. In Am. Mus. 1560 the 

 posterior half of ps, p4 is widely expanded transversely. 

 P4 is submolariform (ap. 23 mm., tr. 15 in the type), 

 with cusps analogous to the paraconid, entoconid, and 

 metastylid of the molars, and a very prominent cusp 

 101959— 29— VOL 1 25 



are sharply pointed and slightly more flattened in- 

 ternally than externally. In m^ the unworn proto- 

 cone and ectoloph measure in height 18 and 31 milli- 

 meters, respectively, exhibiting incipient hypsodonty. 

 They are sharply pointed and closely approximated. 



