O. C. Marsh—Leptilia of the Baptanodon Beds. 405 
Art. XLV.—The Reptilia of the Baptanodon Beds; by 
O. C. Marsa. 
THE Baptanodon beds form a distinct horizon in the Juras- 
sie of the Rocky mountain region, their position being just 
above the red Triassic sandstones, on which they rest uncon- 
formably, and immediately below the Atlantosaurus beds. 
They consist entirely of marine strata of shales, limestones, 
and sandstone, and contain a peculiar invertebrate fauna in 
which Belemnites densus, M. and H., is a characteristic fossil. 
The writer first recognized this horizon and determined its 
Jurassic age, in 1868, near Lake Como, in Wyoming, where 
the strata are well developed, and their geological position is 
clearly defined in the characteristic section at Como Bluff. In 
1870, the writer again found the same horizon in the Green 
river valley, in Utah, on the eastern flank of the Uinta moun- 
tains. Here, also, he discovered the first vertebrate remains 
detected in the horizon, the most characteristic of which per- 
tained to a small crocodile. The humerus was only five 
inches in length. The shaft is slender, and the distal end one 
and one-fourth inches in width. This animal may be referred 
to the genus Yeplosaurus, found in the Atlantosaurus beds 
above, and the species be known as Diplosaurus nanus. 
> 
Figure 1.—Left hind paddle of Baptanodon discus, Marsh. One-eighth natural size. 
Several years later, the writer carried on extensive explora- 
tions in this horizon in the Como region of Wyoming, and 
here was found the skeleton of the large saurian which has 
since given the name to the horizon. ‘This new reptile, nearly 
allied to Jchthyosaurus, but without teeth, was first called 
Sauranodon natans by the writer,* but, as the generic name 
proved to be preoccupied, it was replaced by Baptanodon, 
and at the same time the paddle of a second species was 
figured (vol. xix, p. 491), and this is also shown in figure 1 
above. A vertebra of the type species is represented in figure 2. 
Subsequent researches brought to light a number of other 
specimens in the same region, and still others were obtained 
from more distant localities in the same horizon. 
* This Journal, vol. xvii, p. 86, January, 1879. 
Am. Jour. Sct.—TutrRp Serres, Vou. L, No. 299.—NOVEMBER, 1895. 
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