J. W, HULKE ON ORNITHOPSIS. 759 
the dorsal centra there are but two chambers, which are separated 
by a longitudinal median septum. The neural arches are coossified 
with the centrum throughout the column ; they are extraordinarily 
elevated, and their antero-posterior diameter is small. The zyga- 
pophyses are at its summit, and have extensive articulating surfaces. 
The anterior pair are divided by a deep median fissure, while the 
posterior are united and support, as a pendant from their inferior 
median line, a hyposphen, a structure more fully described under 
the head of Amphicelias, where it 1s equally developed. When the 
vertebrae are in relation, the base of the hyposphen enters the 
fissure between the anterior zygapophyses, and maintains them in 
position. This structure is obsolete in the lumbar vertebre. The 
diapophyses...... of the dorsal vertebre are light, and concave below. 
They are supported by thin osseous buttresses, the most important 
of which are the two inferior ones. The anterior of these is much 
the most prominent, and bears the capitular articular face for the 
rib. In no case is this surface seen on the centrum; but it descends 
somewhat in the posterior vertebra, but not so low as the level of 
the neural canal. The neural spines are rather short, and are set 
transversely to the axis of the animal. The superior portion is ex- 
panded transversely, and in an anterior dorsal vertebra is widely 
emarginate above, so as to appear double’*. With Camarasaurus 
Prof. R. Owen has recently identified (generically ?) his Chondrostco- 
saurus (= Ornithopsis), from British Wealden beds, and on this 
basis has offered a reconstruction of the latter animal. It is to 
me a matter of sincere regret that the material at Prof. Owen’s 
disposal for this was limited to three centra, two very mutilated, 
from none of which was it possible to gain a true insight into the 
construction of the arch and processes. In their opisthoccelous 
form, large lateral foramen, great internal chambers, median parti- 
tion-wall, and magnicellular cancellous tissue and double rib-articu- 
lation, the dorsal vertebrae of Chondrosteosaurus, as Prof. Owen 
points out, exhibit correspondences with those of Camarasaurus & 5 
and this holds equally good with those of Atlantosaurus. Yet, 
with these correspondences, there are differences which cannot be 
quite passed over. In every dorsal vertebra of Ornithopsis known 
to me, the lateral foramen, uuless distorted by pressure, is longer 
than high. In this, Ornithopsis more nearly resembles Anphiceelias 
than Camarasaurus. In Camarasaurus the opening is figured as 
partly in the neurapophysis; this I have never seen in Ornithopsis. 
In their great elongation, and in the long narrow shape of the 
lateral opening, the cervicals of Ornithopsis (Chondrosteosaurus, 
Owen) agree with those of Camarasaurus§ ; but in Ornithopsis the 
hollow is a wide-mouthed pit, contracting towards its bottom, and 
not a linear foramen leading into an inner chamber, as Prof. Cope’s 
* Pal. Bulletin, No. 28, pp. 233-246, from Proc. Amer. Phil. Soc., Dec. 1877. 
+ Annals and Mag. Nat. Hist., 1878, vol. ii. pp. 202-215, pls. x., x1. 
+ Ibid. pp. 201-208. 
§ Owen, wt supra. 
