410 Bulletin American Museum of Natural History. [Vol. XXVII. 



according to certain evidence, an offshoot from ancestors of the Creodont 

 Mesonychidte (as first suggested by Matthew) but the ahernative possibiUty 

 of rehitionship with some Lemuroid-Insectivore group has certain points 

 in its favor. Perissodactyls occasionally parallel Artiodactyls in some 

 features, but the Lower Eocene Artiodactyls and Perissodactyls are widely 

 separated in many seemingly deep seated characters. Certain resemblances 

 to Condylarths are simply primitive Placental characters. 



(2) All the remaining ungulate suborders may be conceived to trace 

 their ancestry back to a varied order of Cretaceous Protungulates. These 

 were primitive Placentals of small size, related to the Creodont-Insectivore 

 stock but probably falling under the original definition of the Condylarthra. 

 There are various possible reasons why such forms have not yet been dis- 

 covered. They may have dwelt in some boreal Holarctic centre as yet 

 unknown; or they may have inhabited the same lands as did the known 

 Cretaceous mammals and dinosaurs, but, being forest dwellers and possibly 

 in part arboreal, they escaped preservation, whereas the known Cretaceous 

 mammals may have dw^elt near the swamps or on the plains. 



(3) By Basal Eocene times the Protungulates had spread into North 

 America, South America, and Europe and had already split up into a num- 

 ber of well separated families. In North America (Puerco and Torrejon) 

 we find Phenacodonts, Meniscotheres, Periptychids and Pantolambdids. 

 In Europe Condylarths (Euprotogonia) and Amblypods (Coryphodon) are 

 recorded by Deperet (1908, p. Ill) in the Thanetian stage. In South 

 America, the Notostylops Beds of Patagonia (which according to all author- 

 ities are at least not later than Basal Eocene) contain ?Condylarths {e. g., 

 Didolodus), ?Periptychids {e. g., Guilielmofloweria) and early specialized 

 members of the Homalodotheria or related groups. 



(4) From different families of this widely distributed Upper Cretaceous- 

 Basal Eocene protungulate order arose in different continents the various 

 groups known as Amblypoda, Proboscidea, Hyracoidea, Perissodactyla, 

 Notoungulata, etc. The Amblypoda may have sprung from North American 

 Pantolambdids; the Hyraces, Embrithopods, Barytheres and Proboscidea 

 may trace their origin to a common Lower Eocene African stock which also 

 gave rise to the Sirenia; the Perissodactyls and Chalicotheres may have 

 been derived from Holarctic Condylarths allied to the Phenacodontidse; 

 one of the South American orders (the Litopterna) may have been derived 

 from South American representatives of the Meniscotheriidse, others (Homa- 

 lodontheres and Astrapotheres, Toxodonts and Typotheres) from small 

 protungulates allied to Henricosbornia and the ancestors of the Notostylo- 

 podise; while from related forms with more distinctly bilophodont molars 

 arose the Pyrotheria. 



