Scott and Osborn — Orthocynodon from the Eocene. 223 



but during a temporary halt and slight re-advance of the slowly 

 retreating ice-sheet which formed the drift without its limits. 



Incidentally the observations herein recorded indicate (1) 

 from the essentially homogeneous and unquestionably uni- 

 partite character of the drift-sheet above the 

 section 6, that the Torrellian hypothesis of the deposit of a 

 ■mine and a superficial moraine by each glacier is in- 

 valid; (2) from the disappearance of the blue coloration down- 

 ward in sections 6, 8 and 10, that this blue color is not normal 

 and changed to brown or yellow by oxidation from above, as 

 urged by Hawes,* Julien,f Von den Bruch,:}: Shaler,§ and 

 others, but is in some way acquired. 



Art. XXIV .— Orthocynodon, an animal related to the Rhinoceros, 

 from the Bridger Eocene ;\ by Wm. B. Scott and Henry F. 

 Osborn. 



le name given to designate a new genus 

 of the Rhinoceros line from the Bridger Beds of Wyoming. 

 It was discovered by the Princeton Expedition of 1878, in the 

 Bad Lands of Bitter Creek. It carries the Rhinoceros line 

 farther back than it has been supposed to exist. The oldest 

 representative of this line known hitherto is Amynodon^ a 

 genus found by Professor Marsh f in the Uintah beds which 

 overlie the Bridger. Orthocynodon was at first referred to the 

 latter genus, until important differences in the molar dentition 

 were discovered. 



Generic characters.— The lower canines are erect and func- 

 tional, giving the name to the genus. The lower incisors are 

 two on each side and semi-procumbent. The lower premolars, 

 with the exception of the first, are somewhat simpler than the 

 molars, but have the Rhinoceros pattern of two inward-open- 

 nts directed forwards. The upper premolars have 

 distinct posterior crescents and small postero-internal cusps. 

 The post-glenoid and post-tympanic processes apparently do 

 not unite to surround the external auditory meatus. There is 

 a sagittal crest separating the temporal fossae. 



This genus differs from Amynodon in the erect canines, in 



ration des Depots superfici 

 : Meteoriques, 1881, pp. 147-168. 



§ Glaciers, 1 



| Description from specimens in the E. M. Mus 



1 This Journal, III, vol. xiv, p. 251. 



