626 Troxell — Vertebrate Fossils of Roclc Creek, Texas. 



moved southward across the newly formed isthmus and was 

 probably already established at the beginning of the Glacial 

 Period. The larger Auchenia, not fitted for other than plains 

 habitation, continued within the barriers which were passable 

 to its smaller cousin and hence became extinct. Its exter- 

 mination resulted, in a more or less direct way, from the 

 advance of the great ice sheet, though the cold itself would not 

 necessarily have accomplished the destruction. It is estimated 

 that a drop of 7° in yearly average temperature would be 

 sufficient to restore Glacial conditions in Europe (16.134). 

 With the ice there came a change of vegetation ; incident to 

 its approach there would be greater precipitation, then swollen 



Fig. 14. 



Fig. 15. 



Fig. 14. Pathologic camel phalanx. Anterior view. One-third nat. size. 

 15. Normal camel phalanx, front and rear views. One-third nat. 



Fig 

 size. 



streams, floods and swampy lands. The region thus became 

 uninhabitable to the animals of arid land adaptation and their 

 extinction followed. So to-day the North American Auchenia 

 is known only by its very abundant fossil remains. 



Much has been said about the effect of diseases in causing 

 the extermination of races. The interesting pathologic phalanx 

 (fig.. 14) is probably a result of exostosis or uncontrolled 

 deposition of bony material. The bone was not broken, 

 because it shows the same length as the normal one (fig. 15) 

 of the same size. Possibly the disease which caused the death 

 of the individual also contributed to the destruction of the 

 species. 



Canidce. 



There were found with the Kock Creek material parts of 

 dog-like animals belonging apparently to four individuals. 



