224 Scott and O shorn— Orthocynodon from the Eocene. 



the possession of a posterior crest, and distinct though small 

 postero-internal cusp on the second and third upper premolars; 

 finally, in the fact that the premolar pattern in both jaws is 

 like that of the molars. In Amynodon the canines are nearly 

 procumbent and the premolars are all unlike the molars. It is 

 singular that this genus, belonging to a more recent geological 

 formation than Achaenodon, should have less of the typical 

 Ehinoceros structure in its molars. 



Orthocynodon antiquus, gen. et sp. nov., 



The specimens consist of the skull and lower jaw of one 

 individual, and a portion of the skull containing the molar 

 series of another. In each the upper canines and incisors are 

 wanting. The lower incisors are close to the canines ; they are 

 semi-erect in position and placed in a quarter circle. They 

 have slight fangs and sharp crowns, with low cingula posteri- 

 orly. The canines are almost trihedral in section and curve 

 upwards and slightly backwards, worn at the back of their 

 pointed tips by the upper teeth. A diastema of two inches 

 separates them from the premolars. The lower premolar- 

 molar series differs onlv in size and minor details from that of 

 The first premolar 



Dental formula, 



ng to a single point and supported • 

 face is irregularly 



two fangs. The inner face is irregul; 



Rhinoceros. Each of the remaining teeth presents two iui- 

 ward opening crescents of similar pattern. The third and 

 fourth upper premolars are preserved in our specimens, and the 

 upper molars are complete. The premolars present an exter- 

 nal longitudinal ridge; from it arise a broad anterior ~"~ J 

 narrow and somewhat low posterior crescent, opening 

 ward; the postero-internal cusps are small. The mola 



h.-K-k-- 



postero-internai cusps ; 



like those of the Rhinoceros in the proportion and disposition 



The Skull is about fourteen inches long and five inches deep. 

 The occipital condyle resembles that of the Indian Rhinoceros. 

 There is a recurved paroccipital process having a long forward 

 union with the post-tympanic The post-lympanic and posl- 

 glenoid processes do not unite as in the modern Rhinoceros. In 

 common with all the Eocene Ungulates there is quite a high 

 thin sagittal crest, and somewhat deep temporal fossa, quite 

 unlike the Indian Rhinoceros. The skull in fact does not 

 resemble that of its modern relative. The parielals are narrow 

 and compressed; the frontals expand into a broad well- 

 rounded snout. We cannot ascertain from our specimens 

 whether the nasals bore protuberances for the support of horns. 

 It seems probable that they did not. 



