VERTEBRATE FOSSILS. 473 



Tlu- ferns numbered fully -JO species, some, as Asplenium erosum (Lx.), 

 being of large size. The must abundant form is probably Aspidium 

 Lakesii (Lx.), which is represented in every collection and often by hun- 

 dreds of examples. There are also a curious new 1 1 vnien<>ph\ Hum and a 

 very characteristic species of Adiantum. both in fruit. 



Conifers, as already stated, wen- very rare, almost the only one being 

 a well-marked species of Ginkgo, known from the fruits. 



The Lauraceae is represented by numerous species of Laurus, Litsea, 

 Cinnamomum, Persea, Daphnogene, etc. There are also representatives 

 of the Comaceae, Caprifoliaceae, Araliaceaa, Sterculiaceae, Sapiudaceae, 

 Aceraceae, Juglandaceae, Rosacese, Leguminosae, Rhamnacese, Magnoliaceae, 

 Tiliaceae, Anonacese, Cupuliferae, Vitacese, Ebenaceae, etc., showing that the 

 flora was a rich and varied one. 



SECTION II.— VERTEBRATE FOSSILS. 



By Othniel Charles Marsh. 



INTRODUCTION. 



In the region of Denver are several well-marked geological horizons, 

 which have been named from the characteristic vertebrate fossils they 

 contain. Some of these are known far to the north, and have also been 

 traced to the south along the eastern slope of the Rocky Mountains, marked 

 in nearly every exposure by the remains of extinct animals that were 

 entombed when the strata were deposited. One horizon in the immediate 

 vicinity of Denver is classic ground to paleontologists, as here were first 

 found the remains of the most gigantic reptiles ever discovered, living or 

 extinct. Some of these horizons, again, are represented in the Denver 

 region only by limited outcrops of characteristic deposits, while others are 

 known by fragmentary fossils alone, derived from strata apparently not 

 exposed there on the surface, hut well developed in adjacent regions, where 

 thev have been carefully investigated. 



