582 



UNGULATA. 



T7TO ^02 —Grinding surface o£ a worn molar of 

 ^'mllopotamus alpMHus (from Flower and 

 Lydekker, after Owen). 



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

 E^ene N. Amer., Bndgev Bed.. ; Choeropotamus Cuv. ; Palaeochoerus 

 iomel ; ListriodonMeyevUhe cusps of the upper and lower molars fuse 

 ^ ' into complete transverse ridges. 



Middle Miocene. Elotherium * 

 Pomel, Eocene and Miocene of 

 Europe 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 

 i f c i p f m f , 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 metatarsals of digits 2 and 3 coalesce into a ^^.^T^^^^^^^ °"c^'^" 

 back is an oleaginous musk gland; only 2 young at a birth; DieoUjles Cuv., 

 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 '^?^^^^, Ca. 



large heavy unwieldy body with a thick 

 skin, with short tetradactyle limbs all 

 the digits of which rest on the groimd 

 and have nail-like hoofs ; milk denti- 

 tion i f c i m ^, permanent, i f c i 

 p 4 m 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. Herbivorous, semiaquatic ; 

 confined to Africa. H. amphibius at- 

 tains a weight of four tons, Africa ; H. 



* Kowalevskv, PalaeontograpUm, 22, 1876. Marsh, Amer. Journ. of 

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



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

 Indian Tertiary and Post Tertiary Vertebrata, Paiacont. Indica, ser. 10, 

 1-4, 1874-87. Filhol, Ann. Sci. Nat. (7), 16, 1893, p. 151. 



Fig. 303. — Hyopotamus {Ancodus) velau- 

 nus Cuv., Oligocene. A anterior, B 

 posterior foot x i. digits numbered, 

 carpals and tarsals marked by initial 

 letters (after Kowalevsky, from Zittel). 



