ART. XXXUL—ON A CARNIVOROUS DINOSAURIAN FROM THE 
DAKOTA BEDS OF COLORADO. 
By E. D. CoPE. 
The vertebrate fauna of the Dakota epoch of the regions west of the 
Mississippi having been heretofore unknown, it is satisfactory to be able 
to state that I have recently received, from a new locality, evidence of 
the existence of some colossal species of Dinosauria during this period. 
This is derived from a skeleton discovered near to the town of Canyon 
City, on the Arkansas River, near the point where the latter issues from 
-the cafion through the Greenhorn Range of the Rocky Mountains. 
At present, I only describe a portion of the right dentary bone, which 
supports eight teeth, and contains a cavity at the anterior extremity, 
from which one tooth was probably shed. The dentition is of the car- 
nivorous type, and does not differ from that of the species of the genus 
Lelaps, to which have been referred numerous species from Cretaceous 
Nos. 5 and 6. The crowns exhibit the gradual {modification of form in 
the succession from rear to front which I have already described in the 
Lealaps incrassatus.* There are subordinate characters ‘exhibited by the 
present animal which show that it is quite distinct from any of the spe- 
cies heretofore known. 
Five successional and two functional teeth exhibit crowns complete, 
or nearly so. The posterior exhibit a nearly straight posterior edge and 
an anterior one curved backward to'a subacute erect apex. Both are 
denticulated, but the denticles of the anterior edge do not descend so 
- near to the base of the crown as those of the posterior. The anterior 
series turns inward toward the base. The section of the crown is here 
(at the ninth tooth from before) not quite symmetrical, the internal 
face being the more convex near the apex. Soon the greater convexity 
of the outer side of the crown near the base becomes apparent, and as 
the inward curvature of the anterior denticulate edge increases, the con- 
vexity becomes more pronounced. On the second tooth, which is the 
first one preserved, the posterior edge is median ; the anterior edge is 
on the inner side of a gently convex anterior face, which passes into the 
external face by an abrupt convexity. The long axis of the section of 
the crown does not connect the cutting edges, but passes from the posterior 
edge to the extero-anterior convexity mentioned, and parallel to the sym- 
physis mandibuli. The enamel is smooth and with a fine silky luster. 
Two stages of succession are evident in these teeth. Successional crowns 
* See Proceedings Academy Phila., January, 1377. a 
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