1884.] The Creodonta. 259 
the inferior true;molars of the Mesonychidze. The second modi- 
fication consists in the addition of lateral cusps or spines to the 
simple cone. Such a type is seen in inferior molars of Spalaco- 
therium tricuspidens Ow., of the Jurassic period, and in some of 
the incisors of Plestadapis tricuspidens' Gerv. This form, by the 
shifting of the two subordinate cusps to the inner side of the 
principal one, will give a trituberculate molar of the lower series, 
an exaggeration of which is seen in the South African “ mole,” 
le 2.—Mandible of Mesonyx ossifragus Cope, from the Wasatch epoch of the 
5 5 Horn river, Wyoming, one-third nat. size. Original. From Report U. S. G, 
v Terrs., Vol. Ill. 
Chrysochloris. If a cingulum appears at the posterior base of 
such a tooth, we have a rudimental “heel,” such as is seen in 
Centetes, and is still better developed in many creodont and mar- 
Supial genera, forming the basis of the inferior sectorial tooth of 
the Carnivora, This, which I have called the “ tubercular-secto- 
1 : i 
Lemoine, Communication sur les Ossemens Fossiles deny. Reims, p. 9, pl. 1, 
13. The superior dentition of this specimen is represented in fig. 6. 
