,-t^ 



- G* 



PALEONTOLOGICAL BULLETIN, 

 No. 21. 



(Read before the Academy of Natural Sciences, April 11, 1867.) *»"" 



On the Geologic Age of the Vertebrate Faunse of the Eocene of 

 New Mexico. — Prof. Cope presented a synopsis of the species de- 

 scribed from the Eocene of New Mexico, arranged in the following 

 manner : — 



Mammalia. 



Perissodactyla 

 Amblypoda 



Pantodonta 

 Incertse sedis 

 Quadrumana 



Prosimice 

 Rodentia. . 

 Insectivora 



Tceniodonta 



Creodonta 



Aves 



Reptilia 



Crocodilia 

 Testudinata 

 Lacertilia . 



Pisces 



Ginglymodi 

 Plagiostomi 



10 



4 



2 



13 



10 

 9 



3 

 10 



*3 

 19 



7 



15 



2 



2 



6 



54 



1 

 24 



This total number of eighty-seven species may be considered in 

 two aspects, viz., in regard to their geological position, and their 

 anatomical structure. 



As regards the former, it may be observed, that the record 

 preserved in these beds is doubtless more imperfect than that 

 found in many others, owing to various physical conditions. One 

 of these is an evident disturbance of temperature and moisture 

 which they have sustained, perhaps in connection with the vol- 

 canic phenomena which played so important a part in New Mexico 

 during the later tertiary times. The fossils are generally found 

 in a fragmentary condition, and often distorted by pressure. The 

 fractures of the surface are often of such a kind as to indicate 

 that the bones have been in a plastic state (see the figures of 

 Stypolophus hians) during which the fissures thus created in 

 them have in many instances been filled with a siliceous limestone. 

 This material now presents a rough external surface of great hard- 

 ness, and sometimes incrusts the teeth in such a way as to render 

 it a difficult matter to expose them. Nodules of the same material 

 abound on the bluffs (see the geological report). Not unfrequently 

 the bones are covered with an incrustation highly charged with 

 the red oxide of iron, and this substance gives its characteristic 

 color to a large percentage of the fossils, the others being gene- 



