UNGULATA. 309 



bones alternate, and the manus is complete (fig. 177). The metacarpal 

 bones are comparatively long and slender, while the phalanges are short 

 and small. The first digit is much the smallest. The femur is short, 

 broad, and flattened, much like that of the ground-sloths, though there is 

 a well-developed third trochanter ; the form and proportions of the tibia 

 and fibula also suggest a comparison with the same animals. The 

 astragalus is a square and flattened bone, with a slightly convex articular 

 surface for the tibia ; it articulates directly with the uavicular and does 

 not touch the cuboid. The pes is complete, with five digits, and the 

 metatarsals are much shorter than the metacarpals ; the intermediate 

 phalanges are also very short and stout. Many specimens of Homalodon- 

 totherium have been obtained from the Santa Cruz Formation of Patagonia, 

 and nearly all the bones of the trunk and limbs have been found at 

 different times in direct association with the skull and teeth. The typical 

 species is H. cunninghami, with a skull about - 5 m. in length. H. segovice 

 is another well-known form of almost equally large size. 



Macrotherium. This genus is known by the greater part of the 

 skeleton found associated with the skull in the Middle Miocene of Sansan, 

 Qers, France ; by another portion of skeleton in undoubted association 

 with the skull in the same formation at La Grive St Alban, Isere ; and by 

 many other fragments from contemporaneous strata both in France and 

 Germany. The skull has a relatively very short facial region, and the 

 orbital cavity is not separated from the temporal fossa. The upper 

 incisors and canines are unknown, but so far as it can be expressed the 



dental formula is !' ;' u '' >m ' ' m ' -_ . The fore limbs are considerably 

 i. 3, c. 1, pm. 3, m. 3 



longer than the hind limbs. The radius and ulna are separate and 

 slender, while the olecranon process of the ulna is small. The femur is 

 destitute of a third trochanter. The bones of the two carpal rows 

 alternate, and the manus comprises only three digits (nos. n, m, iv), of 

 which the outermost is the largest. The hind foot is also similarly 

 tridactyl, with the largest digit outside, but the metatarsals are only half 

 as large as the metacarpals. The typical and best known species, 

 M. magnum, must have been an animal nearly three metres in length. 



Teeth almost identical with those of the Sansan Macro- 

 therium are known from the Lower Pliocene of Eppelsheim, 

 Hesse Darmstadt, and of Baltavar, Hungary ; from China ; 

 from Canada ; and from the Loup Fork Beds (Upper Miocene) 

 of Nebraska, U.S.A. all described under the name of Chalico- 

 therium. An imperfect skull with similar molars (but wanting 

 the snout), from the Lower Pliocene of Pikermi, Greece, and 

 portions of another similar skull (clearly indicating the absence 

 of upper and lower incisors and upper canines), from the 



