134 
MEMOIRS OF THE QUEENSLAND MUSEUM. 
On the right side the walls of the centrum have entirely disappeared. 
The pleurocoele is shown in section, and was originally infilled with matrix 
which was surrounded with very thin peripheral walls. The typically marine 
matrix has now been removed on each side, so far as it is safe to do so. 
The two pleurocceles are not confluent, but the matrix terminates against 
the laminar complex, which forms so distinctive a feature of the centrum, 
within about 20 mm. from the median line. No trace of a median vertical 
partition can be seen in the fractured surface across the centrum, and the 
laminar complex evidently takes the place of this structure. 
Neural Arch. — This region is very incomplete, and the right side has 
largely disappeared. The full height is not preserved, but the fractured surface 
above exhibits a complex of abraded find distorted elements. It is obvious, 
however, that the lamina' and brackets were very extensive and were lightly 
framed. 
The preserved portions present significant similarities in this region with 
those shown in the well-known figure of the vertebra of “ Ornithopsis ” hulkei, 
first described and figured by J. W. Hulke in 1880. 1 
Owing to the presence of an almost complete fracture in the fossil, it 
has been possible to remove the major portion of the neural arch from its 
basal part. The exposed contours give some interesting details of the internal 
structure. From the upper margin of the centrum, near the anterior rim, a 
curved plate, somewhat “ saddle-shaped.” is produced anteriorly and outwardly. 
The basal portion of its anterior surface, when viewed from the lateral aspect, 
arises almost vertically, but the upper portion, as may be seen from impressions 
in the matrix, expands outwardly and anteriorly, evidently supporting 
prezyga pophyses which projected over the border of the contiguous vertebra 
(Plate XVI.). This infraprezygapophysial lamina (to use Osborn and Monk’s 
revised term 2 ), is very incomplete, but it appears to have been much more 
extensive in this vertebra than in other related Dinosaurs, judging from 
impressions in the matrix. Its median portion is incomplete. The base of a 
similar lamina is preserved on the right side, and this meets the base of the 
left lamina above the neural canal. When viewed from above, the fractured 
section shows that the median extension of each lamina curves posteriorly to 
meet its fellow, forming a wide recess above the neural canal. The hypantrum- 
hyposphene articulation is not preserved, but was evidently present above the 
fractured section. 
A large recessed area lies between this anterior lamina and the infra- 
diapophvsial buttress. This recess is relatively very large and attains a depth 
of at least 60 mm. (Text-figure 3). Only the basal part of the median portion 
1 Hulke, J. W., Quart. Journ. Cfeol. Soc., Vol. 30, pp. 32-31, plate iv. 
2 Osborn and Mooli, Mem. Amer. Mus. Nat. Hist, n. s. III., 1921. 
