UNGULATA. 345 



the temporal fossa by a slender bar of bone ; and the jugal element 

 of the robust, outwardly curved zygomatic arch sometimes (if not always) 

 bears a large, downwardly-directed process. The mandible is a little 

 produced downwards at the angle, and it also bears two other bosses 

 on the inferior border, one below the hinder premolars, the other below 

 the canine. The dental series is complete, consisting of the usual 44 

 teeth. The canines are very stout, and the incisors are pointed. All 

 the premolars are simple compressed cones, except the fourth of the upper 

 jaw, which is square and bears two stout conical cusps. The angular 

 cusps of the true molars form two irregular and imperfect transverse 

 ridges on each tooth ; and the hindermost lower molar is destitute of 

 a posterior talon or supplementary lobe. All the teeth except the canines 

 exhibit more or less distinctly a basal cingulum. The limbs are compara- 

 tively long and slender, and remarkable on account of the reduction of 

 both feet to two functional toes. Digits uos. in and iv are fully and 

 normally developed, while nos. n and v are represented merely by the 

 upper end of their respective metapodials, while no. i is entirely absent. 

 The typical European species, Elotherium magnum, is known both by the 

 skull and feet from the Upper Eocene (Quercy Phosphorites) and Lower 

 Miocene (Ronzon, France). An allied form, Elotherium crassum (fig. 197), 

 is represented by the greater portion of the skeleton from the Lower 

 Miocene (White River Formation) of Colorado and South Dakota ; and 

 this animal must have measured not less than two metres in length 

 by more than a metre in height. Other species are known from cor- 

 responding strata in Nebraska and in the Cypress Hills, District of 

 Assinibola, Canada. There is also an allied genus, with orbits not 

 completely surrounded by bone (Achcenodon), in the Middle Eocene 

 (Bridger Series) of Wyoming. A fragment of a large mandible from 

 the Lower Pliocene (Siwalik Formation) of the Punjab, India, also 

 seems to represent a nearly related genus (Tetraconodori). 



Hippohyus. A pig from the Lower Pliocene of the Siwalik Hills, 

 India, in which the cusps of the grinding teeth are unusually deepened 

 and transformed into irregularly radiating, crimped laminae. The skull 

 of H. sivalensis is completely known, and proved to be essentially similar 

 to that of Sus. 



Sus. The true pigs of the genus Sus have always been confined to 

 the three continents of the Old World. The oldest known species is a 

 small form from the Middle Miocene of France and N. Italy (Sus 

 chceroides), with comparatively simple molars much resembling those 

 of the Sus andamanensis now living in the Andaman Islands. S. 

 palceochcenu is another small species from the Lower Pliocene of 

 Eppelsheim, Hesse Darmstadt. There is evidence of larger forms in 

 the Lower Pliocene of France, Greece, the Island of Samos, and the 

 Red Crag of Suffolk (S. erymanthius and others) ; and the existing wild- 

 boar (Sus scrofa) appears first in the Upper Pliocene of Europe. The 



