280 University of California Publications in Geology [Vol. 10 



there is uo fusion of these phalanges. The ungual of this digit is 

 comparable in size with that of Lestodon, and thus both agree in 

 differing from Megalonyx and Scelidotherium. 



The fifth metatarsal in Lestodon resembles that of M. robustus 

 rather more closely than that of M. harlani in flatness of the outer 

 side. The fourth and fifth digits in M. harlani have suffered a re- 

 duction similar to that in Lestodon. 



COMPARISON WITH SCELIDOTHERIUM 



Burmeister states that the calcaneum in Scelidotherium approaches 

 in shape the genera Megalonyx and Nothrotherium rather than Mega- 

 therium and Mylodon. Owen had previously pointed out that "In 

 the Scelidotherium the posterior termination of the calcaneum is 

 broader, and terminated by a less angular convexity than in the 

 Mylodon. . . . " 23 In the thickness of the tuber calcis Scelidotherium 

 is more like other mylodonts and differs from Megalonyx and Nothro- 

 tlu rium, in which the posterior portion of the calcaneum is compressed 

 and fan-shaped. With regard to the second largest of the ankle bones 

 Owen states: "The astragalus of the Scelidotherium agrees with that 

 of the Mylodon in the less depth of the middle division of the upper 

 surface and the more open angle at which it joins the inner convexity. 

 . . . " 24 It has already been pointed out 23 that the inner and outer 

 divisions of the tibial articulating surface of the astragalus are sep- 

 arated by a more distinct angle in M. harlani than in M. robustus. 

 The astragalus in Scelidotherium magnum, as shown by Winge, 20 is 

 unquestionably more nearly like that in members of the Mylodontidae 

 than that in the Pleistocene Megalonychidae. In the less open angle 

 between the confluent articulating surfaces for the tibia the astragalus 

 of this form resembles Mylodon harlani more closely than M. robustus. 



In the pes of Scelidotherium magnum as given by Winge, 27 the 

 internal and middle cuneiforms, with the former of which the first 



23 Owen, R., On the Megatherium, etc., p. 822. See also Owen, Description of 

 the skeleton of an extinct gigantic sloth, Mylodon robustus, etc., p. 133. 



Ibid., p. 821, 1859. See also Owen, Description of the skeleton of an ex- 

 tinct gigantic sloth, Mylodon robustus, etc., p. 132. 



25 P. 269. 



20 Winge, H., Jordfunde og nulevende Gumlere (Edentata) fra Lagoa Santa, 

 Minas Geraes, Brasilien. Med Udsigt over Gumlernes indbyrdes Slaegtskab, 

 E. Museo Lundii., Bd. 3, pt. 2, pis. 41 and 42, Copenhagen, 1915. 



27 Winge, H., ibid., pp. 205-208, pi. 42, 1915. 



