MAMMALIA. 400 



their feet nearly equal, the anterior possessing four or five fingers, and the 

 posterior three or four ; the external fingers were dei)rived of nails. The 

 tail was very long and powerful. 



The genus Megatherium is characterized by its teeth, which are tetra- 

 gonal, and have their crowns transversely furrowed. There are five above 

 and four below on each side. The fibula is soldered to the tibia by both 

 of its extremities. The fore feet have four fingers, the hind feet only three, 

 the two external without nail. Only one species is well known, M. nivieri, 

 from South America. In size this exceeded the rhinoceros. Some frag- 

 ments of Megatherium have also been found in North America, particularly 

 on the coast of Georgia. The Megatherium is supposed to have fed upon 

 the leaves of trees, previously uprooted by the animal. 



The genus Megalonyx is distinguished by its molars, five above and four 

 below on each side, sub-elliptical in form, the crown of which is hollowed 

 in the middle, whilst the edge remains prominent. The anterior limbs are 

 a little longer than the posterior ones, a character which brings them nearer 

 the Tardigrada proper than Megatherium. The tibia and fibula are not 

 soldered together ; the hind foot is obliquely articulated. The tail is stout 

 and robust. The body of Megalonyx was not so heavy as that of the 

 Megatherium, but the habits were very likely the same. The first species 

 known is M. jeffersonii, of the size of an ox. It was found in a cavern in 

 Virginia. A few other species of the same genus have been discovered 

 in South America. 



The genus Mylodon had the heavy form of Megatherium, but with a 

 quite different dentition. The molars, five above and four below, are worn 

 off in plane surfaces. In the upper jaw, the first tooth is sub-elliptical, the 

 second elliptical, and the others triangular with the internal surface furrowed. 

 In the lower jaw, the first is elliptical, the last but one tetragonal, and the 

 last large and bilobated. The form of the head resembles that of Mes:a- 

 therium. The feet are equal, the anterior with five fingers and the posterior 

 with four ; the two external fingers are deprived of nails, the others provided 

 with large phalanges, terminated with semi-conical and unequal nails. 

 Species of this genus are found in South America, as far as the pampas of 

 Brazil {M. darwinii), and also in North America, in a cave in Kentucky 

 {M. harlani). 



The genus Scelidotheruun is nearly allied to Mylodon. The molar teeth 

 are five above and four below. The upper ones are all triangular. In the 

 lower jaw, the first is triangular too, the second and third a little com- 

 pressed, and the fourth large and bilobated. The body heavy and bulky. 

 The complete skeleton is not yet known. Four species have already been 

 discovered in South America. The largest, S. leptocephalon, was an 

 inhabitant of the southern extremity of the continent. The others belong 

 to Brazil. 



The genus Platyonyx, with its skull and teeth similar to Bradypus, 

 recalls to mind the armadillo, but resembles Megalonyx by its skeleton. 

 The character by which it is distinguished from all its congeners consists 

 in the high development of its feet. The fore feet, having five depressed 



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