SUBORDER B 



XENARTHRA 



95 



opening of the alveolar canal in front of the base of the coronoid process or on the 

 outer side of the lower jaw, seldom on the inner side. 



Megalonyx Jefferson (Fig. 117). Occurs in the Pleistocene and cave 

 deposits of North America, also in the Pliocene (Blanco beds) of Texas. M. 

 leptostoma Cope. 



Ameghino and Scott have described from the 

 Miocene of Santa Cruz in Patagonia, a number of 

 smaller forms, Hapalops, Encholoeops, Hyperleptns 



Fig. 117. 



onyx jeffersoni Leidy. Pleistocene of Kentucky. 

 Skull and lower jaw. About i/g. (After Leidy.) 



Fig. 118. 

 Hyperleptiis garzonianus Amegh. 

 Upper Miocene of Santa Cruz, Pata- 

 gonia. Skull, palatal aspect. Vs- 

 (After Ameghino.) 



(Fig. 118), Schismotherium, Megalonychotherium, Analcimorphus and Pelecyodon, 

 etc. Of these Hapalops (Geronops and Parahapalops Ameghino) occurs most 

 abundantly, and comprises the largest number of species ; also it is more 

 completely known. All of these genera have a third femoral trochanter 

 and five digits. Still earlier remains are those of Proplatyarthus Ameghino 

 from the Astraponotus beds, Hapalops from the Pyrotherium beds, and 

 Hapaloides and Proschismotherium from the Colpodon beds of Patagonia. 



Subfamily 3. Mylodontinae. 



Cheek teeth prismatic, elliptical-triangular in shape. Last lower M larger than 

 the rest and two-lohed. The posterior branch of the alveolar canal opens on the outer 

 side of the lower jaw. 



Mylodon Owen (Fig. 119) f M, with short snout and rudimentary 

 premaxillary bone. Zygomatic arch incomplete, with a strongly developed 

 descending process. Manus with five digits and pes with four. Dermal 

 ossifications developed to some extent. From the Pleistocene of Argentina, 

 M. robustus Owen. In North America, in the Pleistocene of all parts 

 of the United States and in Mexico, M. harlani Owen, and M. garmani 

 Allen. 



Paramylodon Brown. |- M^ triangular. Pleistocene of Nebraska and 

 California. 



Lestodon Gerv. Jaw broad in front. Pleistocene of Argentina. 



