O. C. Marsh—American Jurassic Dinosaurs. 255 
Tue TeEeeErn. 
The teeth of Stegosaurus are very numerous, and mostly cylin- 
drical in form. Those from the maxillary figured on plate VI 
may be regarded as typical. The series represented in figure 
4 consists of functional teeth in position, although separated 
from the jaw. The crowns are more or less compressed trans- 
versely, and are covered with thin enamel. e fangs are 
long and slender, and the pulp cavity is continued nearly or 
quite to the crown. The jaws contain but a single row of 
teeth in actual use. These are rapidly replaced as they wear 
out by a series of successional teeth, more numerous than 
hitherto observed in these reptiles. Figure 5, on Plate VI, 
represents a transverse section through the maxillary, immedi- 
ately behind the fourth tooth. The latter is shown in place (1), 
and below it is a series of five immature teeth (2 to 6), in 
‘Warlous stages of development, preparing to take its place. 
These successional teeth are lodged in a large cavity (c), which 
extends through the whole dental portion of the maxillary. 
The teeth in use were loosel implanted in separate sockets, 
and were readily displaced. The entire dental series evidently 
formed a very weak dentition, adapted to a herbivorous life. 
Tar VERTEBRA. 
The vertebree of Stegosaurus preserved all have the articular 
faces of their centra concave, although in some the depression Is 
slight. They are all, moreover, without pneumatic or medullary 
cavities. On Plate VII, a selection from the vertebral series of 
one skeleton is given, which shows the principal forms. Figures 
and 2 represent a median cervical. The other neck vertebree 
cervicals have a small tubercle in the center of each end of the 
centra, a feature seen also in some of the caudals. All the cer- 
Vicals supported short ribs. 
* This Journal, vol. xvii, p. 87. 
