EVOLUTION OF THE SKULL AND TEETH OF EOCENE TITANOTHERES 



263 



t. la. tuberculum ossis lacrimalis. 



XII. foramen condylare (nervus XII). 



z. Sq. processus zygomaticus ossis squamosi. 



7i. Mx. processus zygomaticus maxillae. 



TERMINOLOGY OF THE UPPER MOIAR TEETH 



The accompanying table shows the terms used to 

 designate the upper molar teeth of ungulates: 



Comparative terminology of the superior molar teeth 



All ungulates: Terminology 

 based upon evolution from 

 a tritubercular, bunodont 

 ancestral molar type. Os- 

 born (1888, 1892) 



Primary molar cones: 

 Protocone 



Paracone-. 

 Metacone. 

 Hypocone. 



Intermediate molar 

 cones: 



Protoconule 



Metaconule 



Premolar cones " : 



Protocone 



Deuterocone 



Tritocone 



Tetartocone 



Secondary pillars or 

 styles: 



Parastyle 



Mesostyle. 

 Metastyle.. 

 Hypostyle. 



Secondary crests: 

 Ectoloph 



Protoloph- 

 Metaloph_ 



Valleys : 



Medisinus_. 



Postsinus 



Secondary folds: 



Crochet 



Antecrochet- 

 Crista 



Secondary pits: 



Pre-, medi-, and 

 postfossettes. 

 Gingulum 



Titanotberes: Leidy 

 (1873), Cope (1883), 

 Marsb (1877) 



Antero-external 



lobe. 

 Postero-external 



lobe. 

 Postero-internal 



lobe. 



■' Tubercles "- 



Antero-internal 

 be. 



Buttress 



Median fold 



Basal ridge. 



Horses: Huxley (1876) 

 and Lydekker (1886, 

 p. 67) 



Anterior pillar 



Anterior crescent. 

 Posterior crescent 

 Posterior pillar 



Anterior ridge. 



Middle ridge 



Posterior ridge.. 

 Posterior promi- 

 nence. 



Rhinoceroses: Cuvier (1836), De 

 Blainville (1846), Gaudry (1878), 

 Pavlow (1892) 



Dentioule interne du pre- 

 mier lobe. 



Dentticule externe du pre- 

 mier lobe. 



Denticule externe du second 

 lobe. 



Denticule interne du second 

 lobe. 



Crete externe. 



Colline seconde = Crete ou 



lobe antSrieur. 

 La troisieme colline = crete 



ou lobe post^rieur. 



Vallon oblique 



Fossette post^rieure. 



Crochet. 



Crochet ant^rieur. 

 Antecrochet 



Fossette post&ieure=fos- 



settes. 

 Bourrelet 



Rhinoceroses, English au- 

 thors: Boyd-Dawkins 

 (1867), Busk (1877) and 

 Lydekker (1882), Joote 

 (1874) 



Second costa. 



Costae (in part) 



First costa (buttress) . 



Posterior collis (in 

 part) . 



External lamina (dor- 

 sum). 

 Anterior collis 



Median coUis. 



Anterior valley.. 

 Posterior valley. 



Posterior combing 

 plate (uncus, cro- 

 chet) . 



Antecrochet 



Anterior combing 

 plate = crista. 



Posterior collis (in 

 part) = cingulum, 

 guard. 



Rhinoceroses and 

 ungulates, Ger- 

 man and Russian 

 authors: Riiti- 

 meyer (1863) and 

 Kowalevsky (1873) 



Innenpfeiler 

 des Vorjochs. 



Innenpfeiler 

 des Nach- 

 jochs. 



Pericones, 

 Randgipfeln. 



Aussenwand. 



Vorjoch. 



Nachjoch. 



Wulst. 



■ Premolar cusp; term proposed by W. B. Scott (1891). 



