338 P. S. Lull — Pleistocene Ground Sloth, 



than in Mylodon. The rounded condyles, with the greater 

 part of the articular area on the ventral surface, and the aspect 

 of the foramen magnum, opening obliquely to the long axis of 

 the skull instead of backward, show that the head was carried 

 more at right angles to the vertebral column than in Mylodon. 

 The long calcaneum with posterior end resting flat on the 

 ground, and the astragalar facet looking forward, indicate a 

 primitive foot more flexible at the ankle than in the contem- 

 poraneous Mylodon" 



Of the type species of this genus, P. nebrascensis, Mr. 

 Brown describes at some length the skull, jaws, and bones. of 

 the hind limb and the digits of the maims. 



Doubt has been cast on the validity of the genus Para- 

 mylodon by Osborn,* who says : 



u Paramylodon is described as in some features more, in 

 others less specialized than Mylodon and retaining features of 

 the older, more primitive sloths. It differs from Mylodon in 

 having but four upper teeth. ... A second specimen has 

 recently been found near Walsenburg, Colorado [that described 

 by Cockerell, Univ. of Colorado Studies, vol. vi, pp. 309-312, 

 1909], which contains Ave upper teeth, and while exhibiting 

 the elongate skull and inflated muzzle of the type of Para- 

 mylodon, it indicates that the generic distinction between 

 these two forms may be insecurely founded. A fine specimen 

 of a Mylodon, not distinguishable from the Walsenburg speci- 

 men, comprising most of the skeleton, was found in 1880 by 

 Mr. S. Garman of a Harvard University expedition at Hay 

 Springs [Mylodon garmayii Allen type]." 



Regarding the matter under consideration Allenf says : 



" Concerning Paramylodon, as to the validity of which 

 some doubt has been expressed, it seems that its claims to 

 generic rank are well founded. Its reduced dentition and 

 elongate rostrum, with other characters pointed out by Brown, 

 seem sufficiently trenchant. The contiguity of the astragalar 

 and tibial facets of the fibula, however, can not be considered 

 of generic value, since this condition is also found in M. gar- 

 mani." 



In a paper by Mr. Chester Stocky on the Rancho La Brea 

 skulls, twenty-seven of which are now in the collection of the 

 University of California, the author expresses the following 

 opinion : 



" The nineteen skulls from Rancho La Brea are similar to 

 the Nebraska and Colorado specimens in the elongation of the 



*Osborn, H. F., The Age of Mammals, p. 457, 1910. 



f Allen, op. cit., p. 344. 



% Stock, C, Science, new ser., vol. xxxix, p. 762, 1914. 



