582 



UNGULATA. 



Fig. 302. — Grinding surface o£ a worn molar of 

 Hippopotamus amphibius (from Flower and 

 Lydekker, after Owen). 



families : Achaenodon Cope ; Homacodon Marsh (Pantolestes), Middle 

 Eocene, N. Amer., Bridger Beds. ; Choeropotamus Cuv. ; Palaeochoerus 

 Pomel ; Listriodon Meyer, the cusps of the upper and lower molars fuse 



into complete transvei'se ridges. 

 Middle Miocene. Elotherium * 

 Pomel, Eocene and Miocene of 

 Em'ope and America, with com- 

 pletely enclosed orbit, with two 

 complete toes, digits 2 and 5 

 being represented only by their 

 metapodia, last molar without a 

 supplementary lobe. 



Fam. 2. Dicotylidae. Peccaries 

 * ifcipf^fj upper canines 

 directed outwards, the last pre- 

 molar nearly as complex as the 

 molars, only three toes on pes ; 

 stomach 3-chambered with oeso- 

 phageal groove ; the metacarpals 

 and rnetatarsals of digits 2 and 3 coalesce into a cannon bone, on the 

 back is an oleaginotis musk gland ; only 2 young at a birth ; 2 species. New 

 World, from Texas to Patagonia. Many extinct species Pliocene and 

 Pleistocene of Amer. 



Fam. 3. Hippopotamidae.t Skin 

 almost hairless ; with huge head and 

 large heavy unwieldy body with a thick 

 skin, with short tetradactyle limbs all 

 the digits of which rest on the grovmd 

 and have nail -like hoofs ; milk denti- 

 tion * f c T m 5, permanent, ^ f c | 

 p f wi f, premolars simpler than 

 molars ; molars with four tubercles 

 which wear down so as to present a 

 double trefoil pattern (Fig. 302) ; last 

 lower molar trilobed. Incisors tusk- 

 like, rootless ; canines large, curved, 

 rootless. The orbits are tubular and 

 nearly completely enclosed ; tympanic 

 large and ankylosed with the approxi- 

 mated post-tympanic and postglenoid 

 processes of the squamosal. Scapula 

 with a short acromion, ulna and fibula 

 complete. Brain not richly convoluted. 

 Stomach very large, with three com- 

 partments. No caecum. Kidneys lobu- 

 lated. Mammae inguinal. Scrotum 

 absent. Herbivorovis, semiaquatic ; 

 confined to Africa. H. amphibius at- 

 tains a weight of four tons, Africa ; H. 



* Kowalovsk-s', Palaeontographica, 22, 

 Science (3), 48,' 1894, p. 407. 



f Falconer, PaXaeontological Memoirs, 1 and 2, London, 1868. Lydekker, 

 Indian Tertiarv and Post Tertiary Vertebrata, Palacont. Indica, ser. 10, 

 1-4, 1874-87. ' Filhol, Ann. Sci. Nat. (7). Ki, 1893, p. 151. 



\ 



Fig. 303. — Byopotarrms (Ancodus) vdau- 

 nus Cuv., Oligocene. A anterior, B 

 posterior foot x \. digits numbered, 

 carpals and tarsals marked by initial 

 letters (after Kowalevsky, from Zittel). 



1876. Marsh, Amer. Journ. of 



