604 LAND MAMMALS IN THE WESTERN HEMISPHERE 



lar ossicles have been found in association with several skele- 

 tons of \Mylodon. The habits, diet and mode of feeding of 

 the latter were no doubt essentially similar to those of \Mega- 

 therium, but '\Scelidotherium, which had a much shorter and 

 lighter tail, was probably more quadrupedal and browsed 

 upon low shrubbery. 



The third family, the fMegalonychidae, was scantily 

 represented in the Pleistocene of South America, but relatively 

 common in North America. \Megalonyx was, on the whole, 

 less specialized than '\Mylodon or ^Megatherium, but had a 

 strong resemblance to both of them. The teeth, | in number, 

 had the foremost one in each jaw separated by a considerable 

 space from the others and more or less tusk-like in form ; 

 the grinding teeth were worn smooth, without ridges, and of 

 somewhat trihedral shape. The skull was short, broad and 

 deep, resembling in shape that of the tree-sloths ; there was a 

 long, but feebly developed sagittal crest, and the orbits were 

 widely open behind, with hardly a trace of any posterior boun- 

 dary. The muzzle was very short and broad and abruptly 

 truncated and the premaxillary bones were extremely small. 

 The lower jaw was short, thick and massive, with very broad 

 symphysis and almost vertical chin. Neck, body, tail, shoulder 

 and hip-bones did not differ sufficiently from those of ^Mega- 

 therium to require particular notice. 



The fore limb was shorter and more slender than the hind ; 

 the humerus had the epicondylar foramen and the very massive 

 femur retained the third trochanter ; the tibia and fibula 

 were separate. The feet had five digits, three of which carried 

 claws ; the calcaneum was very peculiar, not at all like the 

 massive, club-shaped bone of ^Megatherium and ^Mylodon, but 

 long, comparatively thin and sickle-shaped. Nothing in the 

 skeleton suggests that the creature's habits differed in any im- 

 portant way from those of the genera last named. 



'\Megalocnus, of the Cuban Pleistocene, a member of this 

 family, was apparently peculiar to the island and was prob- 



