50 



GUIDE TO THE FOSSIL MAMMALS AND BIRDS. 



Pier-oases 



20, 21. 



Table-case 



11. 



Pier-ease 

 20. 



arranged in three sub-orders, are nearly all different from 

 any found elsewhere. The South American llamas, deer, 

 peccaries, tapirs, extinct horses and mastodons, of course, are 

 not indigenous, but passed south over the newly emerged 

 isthmus of Panama or other land-bridge at the beginning of 

 the Pliocene period. 



Some of the earliest known South American hoofed 

 mammals, such as Pyrotherium, are very little different from 

 the Amblypoda and Condylarthra of the northern hemisphere. 

 Plaster casts of jaws, teeth, and feet of Pyrotherium from 

 Patagonia are exhibited in Pier-case 20. The later forms, 

 however, are peculiar in the folding and complication of 

 their often persistently-growing teeth ; also in the structure 



Fig. 40. — Skeleton of Pfaenacodus primsevus, as now mounted in the 

 American Museum of Natural History, New York. 



Pier-case 



20. 



Case T. 



of their feet when they begin to become plain-dwellers and 

 mimic the rhinoceroses and horses of the rest of the world. 

 Toxodon (Fig. 41) is an especially remarkable beast with 

 ever-growing powerful cutting and grinding teeth, well seen 

 in actual specimens in Pier-case 20. A plaster cast of a 

 reconstructed skeleton of this large animal from the Pampa 

 of the Argentine Eepublic, now in the La Plata Museum, is 

 mounted in a special Case marked T. When alive it must 

 have been shaped much like the contemporaneous rodents 

 and giant armadillos. It was preceded in time by Nesodon 

 and other smaller kinds of which remains are shown in 

 Table-case 11. Macrauchenia, also from the Pampa Forma- 

 tion, was a large animal shaped liked a llama, but with three 



