l8o Bulletin American Museum of Natural History. [Vol. X, 



3. — Systematic Revision. 



Order AMBLYPODA Cope 



Most primitive order of Ungulates known. Brain very small, with smooth 

 cerebral hemispheres, large olfactory lobes and exposed cerebellum. Dentition 

 brachydont : Superior molars triangular (tritubercular, bunodont, selenodont, 

 lophodont), rarely with functional hypocone. Ffct pentadactyl, isodactyl ; plan- 

 tigrade (as in Bear) to subdigitigrade (as in Elephant). Displacci?ient in carjuis 

 (unlike Diplarthra) ; lunar resting on unciform only; in tarsus (like Diplar- 

 thra), astragalus resting on cuboid. A tibiale tarsi. Astragalus perforated or 

 grooved. 



The three suborders ;ire very widely separated. 

 SuBoRDiNAL Characters. 



Taligrada Cope 

 Dentition. 

 Typical Eutherian form- The same. 



ula. 

 Molars tritubercular 



selenodont. 

 Premolars simple, with 

 two crescents. 



Skull. 



Nasals, frontals and 

 parietals smooth. A 

 sagittal crest. No alis- 

 phenoid canal ; no air 

 cavities. 



Limbs. 



Plantigrade. An entepi- 

 condylar foramen. A 3d 

 trochanter. An os-cen- 

 trale. Fibula articulat- 

 ing with calcaneum. 

 Astragalus with neck. 



Panlodonta Cope. 



Lopho-selenodont. 



Premolars simple, two 

 crescents. 



Rudimentary parietal 

 horns. Cranium flat- 

 tened. No alisphenoid 

 canal. Air cavities. 



Semi-plantigrade. No en- 

 tepicondylar foramen. 

 A 3d trochanter. No 

 os-centrale. Fibula ar- 

 ticulating with calca- 

 neum. Astragalus 

 without neck. 



Ditioicrata Marsh. 



No superior incisors. 



Lophodont. 



Premolars submolari- 

 form. 



Nasal, maxillary and pa- 

 rietal horns. Cranium 

 flattened. An alisphe- 

 noid canal. Aircavities. 



Sub-digitigrade. Ente- 

 picondylar foramen. A 

 3d trochanter. Os-cen- 

 trale wanting. Fibula 

 not articulating with 

 calcaneum. Astragalus 

 without neck. 



