Y99 
1877.] 233 [Cope. 
On the Vertebrata of the Dakota Epoch of Colorado. 
By E. D. Cope. 
(Read before the American Philosophical Society, December 21, 1877.) 
Not long since I was informed by the Superintendent of Public Schools 
of Fremont County, Colorado, Mr. O. W. Lucas, that he had discovered 
the bones of an enormous saurian at an outcrop of the rocks of the Dakota 
group not far from Canyon City. I encouraged him to proceed with the 
exploration, and asked him to send some specimens which would explain 
the character of his discovery. One of the first objects sent, is a fragment- 
ary lower jaw of a carnivorous dinosaurian, which he found on the surface 
of the ground. This fossil was found to belong to a species heretofore un- 
known, which I referred to the genus Zaelaps, under the name of Laelaps 
trihedrodon.* The second sending included a number of vertebra, which 
apparently represent a much more gigantic animal, and I believe the largest 
or most bulky animal capable of progression on land of which we have 
any knowledge. This reptile I described in my paleontological bulletin 
No. 26, under the name of Camarasaurus supremus. Subsequent send- 
ings included many of the more important bones of the skeleton, which 
render it comparatively easy to determine the general character of this 
monster. Later collections received from Mr. Lucas include the teeth of 
two large species of a new genus which has been characterized under the 
name of Cuulodon ; and the vertebre of three genera new to science, 
which I have named Tichosteus, and Symphyrophus. We also pro- 
cured remains of two additional forms of gigantic size, fit rivals of the 
Camarasaurus, which I referred to the new genus Amphicelias. A spe- 
cies of tortoise was associated with these saurians, and appears to have been 
abundant. It is the oldest species of the order yet obtained from Ameri- 
can formations, and is not very different from existing forms. 
The above named genera are the only ones from the Dakota horizon of 
this continent which have been defined, up to the present time. 
The species of Camarasaurus and Amphicelias, which attained to the 
most gigantic proportions, are remarkable for the light construction of the 
vertebree anterior to the tail. In both genera the centra of the dorsal ver- 
tebra are hollow, including two large chambers which are separated by a 
longitudinal median wall, and which communicate with the cavity of the 
body by a foramen on each side. They are also remarkable for the enor- 
mous elevation of the superior arches, and diapophyses, the result of which 
is to give the ribs an unusually elevated basis, and the cavity of the body 
much space above the vertebral axis on each side. On the other hand the 
bones of the tail and limbs are solid or nearly so, in great contrast with 
some of the Dinosauria of later geological periods. Another peculiarity of 
the genus Camarasaurus at least, is the probable great length of the an- 
* Bullet. U.S. Geol. Surv. Terrs. ITI, 1877, p. 805. 
PROC. AMER. PHILOS. soc. xviI. 100. 2D. PRINTED JAN. 12, 1878. 
