O. C. Marsh—- American Jurassic Dinosaurs. 419 
is region, but 
expanded. The vertebree in this region, as in all the known 
Sauropoda, have the peculiar diplosphenal articulation. This 
is shown in figure 2. In the vertebra figured, at the base 
of the neural spine, there is a strong anteridg projection, 
which was inserted into the cavity between and above the 
posterior pieepeptyns of the vertebra in front. There appa 
e lumbar vertebrae, as those near the sacrum sup- 
ported tee ribs of moderate size. These vertebree have both 
faces of the centrum nearly flat or biconcave. 
Tue Sacrum. 
cavity it contained. This was divided in part oe a median 
longitudinal partition, as shown in Plate tar i 
m, however, was not continuous the fh janet of = 
sac chien, so that the two lateral cavities were virtually on 
This extended even into the lateral processes. The caasices 
partitions formed by the ends of the respective sae were 
also aged so that the sacrum proper was tially a 
Another peculiar character of the sacrum in the present 
nus is its lofty neural s spine. This is a thin vertical plate of 
ne with a thick massive summit, evidently formed by the 
* Prof. Cope, mistaking the eet of these vertebra in an allied form, 
described them as Ai gine wean w genus, Amphicelias, and even a new 
family, Amphiceliide. (Proc. Am. Phi. Soc, xvii, 243) All the known 
Sawropoda, however, have similar vertebre, with opisthoccelian centra in the 
cervical and anterior dorsal regions. 
+ This Journal, xiv, 87, July, 1877. 
