LETTER OF TRANSMISSION. 
PniLADELPiiiA, June 10, 1876. 
Sir : I send herewith the report on the extinct Vertebrata obtained 
in New Mexico by the United States Geographical Surveys West of 
the One Hundredth Meridian, under your direction, during the sea¬ 
son of 1874. By means of the provision which you placed at my dis¬ 
posal while acting in the field as paleontologist, I was enabled to procure 
the results which are here set forth. 1 present you with a brief synopsis 
of these, which may be included under two heads: stratigraphical and 
paleontological. 
Of stratigraphical results, I may mention three : first, the elucidation 
of the structure of the western slope of tlie Rocky Mountains and the 
plateau to the Avestward of them, in Northwestern New Mexico; secondly, 
the determination of the fresh-Avater character of the “Triassic” beds in 
that region; thirdly, the discoA^ery of extensive deposits of the Lower 
Eocene, equivalent to the Suessonien of Western Europe. 
The paleontological results are numerous. They are included in the 
determination of the faunse of four periods, in basins Avhich had not pre¬ 
viously been explored, viz: in the Trias, the Eocene, the Loup Fork epoch, 
and the Postpliocene of the Sandia Mountains. The first vertebrate fossils 
CA^er determined from the Trias of the Rocky Mountains are included in 
the report. The first discovered Avere obtained by Professor NeAvberry 
while attached to Captain Macomb’s expedition, and are noAv described for 
the first time. The determination of the ages of the respective horizons 
necessarily folloAvs the first determination of the fossils. 
