16 



which is considered distinct from the Brazilian species. This 

 circumstance leads naturally to the question of the specific 

 identity of all these animals with those now living in the same 

 locality, and with the domesticated species. And here I confess 

 the difficulty to be almost insuperable, or at least hardly ap- 

 proachable in the present state of our science, when the views 

 of naturalists are so divided as to what are species among the 

 genera bos, ovis, capra. For myself, I entertain doubt respect- 

 ing the unity of origin of the domesticated horses. But what- 

 ever be the final result of this enquiry, this much is already 

 established by the fossils you have collected, that horses, hogs, 

 bulls and sheep were among the native animals of North Ame- 

 rica, as early as the common American deer, the opossum, the 

 beaver, the musk rat, etc. What remains to be settled respecting 

 their specific identity is involved in the controversy now carried 

 on between naturalists, who admit specific distinctions upon a 

 very wide range of differences, and those who limit them within 

 narrow boundaries. But the final solution of this point can in 

 no way lessen the interest of your discoveries. 



Should j^ou publish anything 1 upon this subject, let me have 

 your notice, for I am deeply interested in the subject, as I always 

 shall be, in everything you do. 



Ever truly your friend, 



L. AGASSIZ. 



CATALOGUE OF MAMMALIA FROM THE TOST-PLEIO- 



CENE. 



Extinct Species. — Mastodon, Megatherium, Megalonyx, Glyp- 

 todon, Mylodon and Hipparion, 2 species. 



Not now Found on the Atlantic Coast, but Indigenous to North 

 America. — Bison, Tapir, Peccary, Beaver, Musk rat, and Elk. 



The Deer, Raccoon, Opossum, Rabbit and the following Domes- 

 tic Animals — Horse, Hog, Sheep, Dog and Ox are not distin- 

 guishable from the living species. 



