50 MEMOIRS OF THE CARNEGIE MUSEUM 
It is easy to see how the shght emarginations at the summit of the neural spines 
in the anterior dorsals and posterior cervicals of H. utterbacki might become succes- 
sively more and more emphasized until they became actually bifid, at least to the 
extent that obtains in Morosaurus. Nor is it impossible that*while specialization 
was taking place along this particular direction, the centra, transverse processes, etc., 
may have assumed a more and more complicated structure. It is by some such 
process as this that the present author conceives that Morosawrus was developed 
from some earlier and more primitive form which was alike ancestral to that genus 
and Haplocanthosaurus, the latter, however, being less progressive than the former, 
became less modified and preserves more nearly the general form and character of 
their common ancestral stock. a 
Although representatives of both genera lived contemporaneously, as is shown 
by the presence of undoubted remains of both in the Canyon City quarry, it is more 
than probable that Morosaurus long survived the other since remains of that genus 
are abundant near the top of the Jurassic in southern Wyoming while as yet no 
remains of Haplocanthosauwrus are certainly known to have been obtained there. 
RELATIONS oF HAPLOCANTHOSAURUS TO EUROPEAN AND SoutH 
AMERICAN Forms. 
As yet we have only discussed the relations of the present genus with North 
American representatives of the Sauropoda. It now remains to notice briefly the 
relations of this genus with certain forms from Europe and South America with 
which it seems to show some relationships. 
Chondrosteosaurus compared with Haplocanthosaurus. 
The characters exhibited by the vertebral centra of Haplocanthosawrus are some- 
what similar to those shown in Chondrosteosawrus gigas Owen, founded on the cen- 
trum of an anterior dorsal or cervical vertebra from the Wealden of the Isle of 
Wight and described and figured in Supplement (No. VI.) to the Monograph of the 
Fossil Reptilia of the Wealden and Purbeck Formations ; pp. 5 to 7, Plates LI-V, of 
Owen's British Fossil Reptiles, London, 1876. 
This resemblance is especially apparent in Plate II., Fig. 2, and Plate V., Fig. 1 
of the paper just cited. However the resemblances shown are not of a character 
which would indicate a closer relationship between Chondrosteosawrus and Haplo- 
canthosaurus than between the former of these with any one of several other genera 
of the Sauropoda. Nor is it possible, owing to the fragmentary nature of the ma- 
terial upon which that genus was based, to decide with certainty even as to just 
