21(3 S. CALVIN AFTONIAN MAMMALIAN FAUNA II 



respondence is perfect. Length of the Turin radius, 16% inches ; greatest 

 width, which is near the distal end, 3^/2 inches. The tibia from Missouri 

 Valley is not perfect. The shaft is complete, and parts of the articulating 

 surfaces at each end remain, but more or less of the great expansions at 

 both extremities have been broken off. The parts left agree with the de- 

 scriptions and dimensions of the tibia of Megalonyx jeffersoni given by 

 Leidy. The patella and ungual phalanx from Sioux City agree likewise 

 with the corresponding parts of the species named; there is little doubt 

 that one of the Aftonian ground sloths is the Megalonyx jeffersoni. 



Description of Plates 

 Plate 18. — Aftonian Fossils 

 Right Half of lower J mo of Bear. 



From Aftonian gravels, Cox pit, Missouri Valley, Iowa. About seven-eighths 

 natural size. 



Plate 19. — Aftonian Fossils 

 FiGLTRES 1-4. — Foot Bones and superior nuerupted Molar of small Horse. 



From the gravels near Thayer. 

 Figures 5-7. — Outer, lateral and croivn Views of upper Molar of Hipparion. 



From Rockport, Missouri. 

 Figure 8. — Proximal Phalanx of Camel. 



From Hiuton Station, Iowa. 

 Figure 9. — Second Phalanx of. prohaMy the same Species as 8. 



From Turin, Iowa. 

 FiGUBE 10. — Premolar of Camel. 



From Rockport, Missouri. (All figures natural size.) 



Plate 20. — Aftonian Fossils 

 Grinding Surface of last right upper Molar of Elephas primigenius. 



From Gravels of uncertain age at Denison, Iowa. About nine-fourteenths 

 natural size. 



Plate 21. — Aftonian Fossils 

 Left Ramus of Mastodon americanus. 



From Aftonian beds. Cox pit, Missouri Valley, Iowa. Slightly more than 

 one-fifth natural size. 



Plate 22. — Aftonian Fossils 

 Upper View of imperfect Mandihle of the American Mastodon. 



Showing the much worn and deeply concave last molars and the wide fissure 

 in each molar due to splitting while the teeth were still in use. 



Plate 23. — Aftonian Fossils 

 Inner and outer Views of lower Incisor of Castoroides ohioensis. 

 From sands, probably Aftonian, near Oakland, Iowa. Natural size. 



Plate 24. — Aftonian Fossils 

 Ulnar and anterior Vietvs of right Radius of Megalonyx jeffersoni. 



From Aftonian sands, Elliott pit, Turin, Iowa. About seven-sixteentha 

 natural size. 



