THEROPOD DINOSAUR GEN. ET SP. INDET. 
A single tooth of a carnivorous dinosaur (Yale Museum Cat. No. 415) was present 
in the quarry in association with the Barosaurus skeleton (see Fig. 2, 16). It is lightly 
constructed, sharply curved, and a portion of the hollow base filled with matrix is 
preserved. Serrations on the anterior convex border can hardly be seen with the naked 
eye but are nevertheless discernible for nearly half the preserved length from the tip. 
On the after concave border they are more pronounced but still minute, and extend 
for the entire present length of the tooth. 
While this tooth has not with certainty been identified, it is comparable in size and 
curvature to certain ones in the after portion of the maxillary of the Allosaurus fragilis 
skull preserved in the American Museum of Natural History, but this is rather slender 
evidence upon which to base an identification of so generalized a tooth. The dimensions 
are: 
mm. 
Total length preserved 26 
Anteroposterior diameter at base 10.7 
Transverse diameter at base 4.7 
RELATIONSHIPS 
Comparison with Diplodocus. — It is evident that Barosaurus lentus represents a 
highly specialized sauropod dinosaur, ponderous of limb, the relative proportions of 
which unfortunately can not be ascertained from the single known specimen. The 
preserved elements compare most nearly with those of Diplodocus, but differ remarkably 
in certain proportions. These resemblances may have been in part convergent and 
merely similar mechanical adjustments of bony tissue to meet similarly disposed strains 
and stresses, and as such imply no close relationship. Among the points of agreement are 
the general proportions of the vertebrae, although as one goes toward the tail the relative 
height of the neural spines grows less in Barosaurus. Pleurocceles are similar in dis- 
position and their proportions are somewhat alike. The caudals of both Barosaurus and 
Diplodocus are also alike in having a concavity in the ventral surface of the centrum. 
There is also a general similarity of the chevrons and of the arrangement of the laminae 
of the vertebra throughout the series. Indeed, two of the distinctive features of Diplod- 
ocus as set forth in Marsh's original description are the presence of the excavation on 
the ventral surface of the caudal centra and the two-branched character of the 
chevrons, upon which the name Diplodocus (&7rXo'o?, double, + 8o/c6s, rafter) is 
founded and which Marsh says distinguishes the vertebral column from that of all 
other Sauropoda. These do not, however, serve to distinguish Diplodocus from Baro- 
saurus. The third point, the elongated caudals in the former, is a distinction. 
The main general differences between Barosaurus and Diplodocus may be sum- 
marized as follows: Details of the lamina of the vertebra, simple character of the 
