232 0. C. Marsh — Footprints of Jurassic Dinosaurs. 



Other genera of carnivorous Dinosaurs are known to have 

 lived in Jurassic time in the same region where these footprints 

 were made, and among them Creosaurus and Labrosaurus 

 would probably have left similar tracks, although the structure 

 of their feet is not accurately known. Ceratosaurus, another 

 carnivorous form, must also be considered, although not 

 known from the region where the footprints occur, while 

 Coelurus is much too small to have made any of the impressions 

 yet discovered. Figures 2 and 3 below show the bones of 

 hind feet of Oamptosaurus and AUosaurus, the Dinosaurs 

 above mentioned. 



2. 3. 



Figure 2. — Left hind foot of Oamptosaurus dispar, Marsh. 

 Figure '6.— Left hind foot of Allosaurus fragilis. Marsh. 

 Both figures are one-twelfth natural size. 



One point worthy of mention is, that both Oamptosaurus 

 and several of the carnivorous forms are known to possess, in 

 addition to the three birdlike main digits, a rudimentary toe 

 on the inner side of the hind foot, representing the first digit. 

 This toe, however, was too short to make an impression in 

 ordinary walking on the ground, but might leave a mark 

 where the surface was very soft. No indications of such 

 marks have been found with these footprints, however, and 

 could hardly be expected under the circumstances. 



The fossil footprints here described were found by H. F. 

 Wells, in 1898, in the Atlantosaurus beds, on the southwestern 

 border of the Black Hills in South Dakota. The specimens 

 are now deposited in the Yale Museum. . 



Yale University, New Haven, Conn., 

 February 21, 1899. 



Explanation of Plate V. 



Footprints of Jurassic Dinosaurs from the Black Hills, South Dakota. 



One-sixth natural size. 



