May 16, 1884.] I [Cope . 



H"! \ 



The Extinct Mammalia of the Valley of Mexico. By E. D. Gope. 

 (Bead before the American Philosophical Society, May 16, I884. ) 



The following study is based primarily on an examination of the speci- 

 mens contained in the Museum National of Mexico, which I was permit- 

 ted to make through the kindness of the Director of the Departments of 

 Geology and Mineralogy, Professor Mariano Barcena. Through the me- 

 diation of the same gentleman, I obtained permission from Professor 

 Antonio Castillo. Director of the School of Mines, to examine the corres- 

 ponding material preserved in the fine museum of that institution. The 

 knowledge derived from the study of the latter, reinforced the results I 

 obtained from the study of the specimens of the Museum National, so as to 

 enable me to reach definite conclusions as to the definitions of various 

 species which are represented in both collections. I wish to record the 

 obligations under which I have been laid by both of these distinguished 

 gentlemen. I have, through their aid, been enabled to make a comparison 

 between the pliocene fauna of Mexico, and that of Buenos Ayres, and 

 that of Oregon. The species of the Pampean fauna contained in. my 

 private collection, are those exhibited by Messrs. Ameghino, Larroque 

 and Brachet, at the Exposition of Paris of 1878. My Oregon material is 

 derived from the explorations of my parties under Messrs. Sternberg and 

 Duncan, and those of Professor Thomas Condon of the University of 

 Oregon, who kindly lent me his collection. 



The collections of the museums of the City of Mexico, above mentioned, 

 are derived from the locality Tequixquiac, and the specimens referred to 

 in the following pages are to be understood as having been derived from 

 that locality unless otherwise stated. Tequixquiac is situated on the 

 northern edge of the valley of Mexico, north of the City of Mexico and 

 the town of Zimpango, and east of the gorge of Nochistongo. 



