378 



R. S. Lull — Pleistocene Ground Sloth, 



cular is pierced in its approximate center by a large foramen 

 for the entrance of nutrient blood-vessels, and this occupies 

 the same relative position in both specimens. Externally the 

 navicular is bounded by a flattened synovial area, somewhat 



Fig. 14. 



Fig. 14. Naviculars of Mylodon harlani. One-fourth nat. size, a, b, 

 No. 10265, Mylodon type with concave astragalar facet, of. c, d, No. 10266, 

 Paramylodon type with conical boss in astragalar facet articulating with 

 depression seen in fig. 13 a, nf. ext. cun, facet for external cuneiform ; cub, 

 cuboidal facet. 



lunate in outline, which bore against the cuboid. This also 

 has approximately the same form and extent in both specimens. 



Di 



imensions. 



10265 



10266 



Eatio 



Thickness, greatest 



Antero-posterior diameter. 

 Transverse diameter 



mm 



28 

 15 

 60-5 



mm 



31 

 75 '5 

 56* 



111- 



101- 



92 



* Somewhat abraded. 



Calcaneum. — One very imperfect left calcaneum is present, 

 showing few characters other than the astragalar and cuboidal 

 articular surfaces. Of these the former, which may not be 

 quite perfect, is sub- triangular and presents a somewhat twisted 

 surface, convex in its long (antero-posterior) dimension and 

 concave in the short transverse one. Anteriorly this surface 

 is confluent with the cuboidal facet, but separated therefrom 

 by a pronounced angle, straight when viewed directly from 

 above, concave when viewed from the side. Adjacent to this 

 ridge on the postero-external side is a deep incision into the 



