FOSSIE VERTEBRATES —REPTILIA 635 
Utah. These remains were named by Professor Cope Dystro- 
pheus.” 
Flallopus, from the Jurassic of Colorado, is remarkable for its 
development as a leaping form; the femur is much shorter than 
the fore part of the leg and the metatarsals are greatly elongated, 
as in the jumping rodents. The whole form was not much larger 
than a rabbit. 
Celurus, from the upper Jurassic of Wyoming, was much 
larger than the preceding genera, being several feet in length. 
It was of the same jumping type, the fore feet being much the 
larger. The skull is very imperfectly known. The most 
remarkable thing about the skeleton is the thinness of the 
bones and the great cavities that exist in all of them, the ribs 
even being hollow. The limb bones, the vertebrae, the bones of 
the pelvis and of the pectoral girdle, are all excavated by large 
air cavities that must have rendered the skeleton very light. 
The dentition was of the same carnivorous type as the former 
genera. 
Ceratosaurus, from the upper Jurassic of Colorado, is one of 
the largest of the Theropoda, being about seventeen feet in length. 
The head was very large in proportion to the body and was 
quite lizardlike in many respects; there was developed on the 
anterior portion of the snout astrong bony process that undoubt- 
edly supported a horn during the life of the animal. The bones 
of the skeleton are very light, having internal cavities such as 
exist in Hallopus and Celurus, only to a less extent; the hind 
limb is much larger than the fore limb, so much greater that it 
is possible that the fore limb was never used for other purposes 
than those of seizing and holding the prey of the Dinosaur. The 
bones of the pelvis are anchylosed together, instead of showing 
the sutures between the bones as in the other forms; this is an 
essentially birdlike feature. 
Allosaurus, Creosaurus, and Labrosaurus are all from the upper 
Jurassic of Wyoming and Colorado. The former was one of the 
largest carnivorous forms of the United States, if not the largest. 
The total length was about twenty-one feet. Remains that have 
