OF HYPSILOPHODON FOXII. 
1045 
Dorsal and lumbar vertebrae* (Plate 74, figs. 11, 12 ; Plate 76, fig. 2).—In passing 
from the front to the foot of the neck, the convexity of the anterior and the concavity 
of the posterior articular end of the centrum decrease. Centra in the anterior dorsal 
region have their anterior articular end plane or slightly concave, and their posterior 
end somewhat more concave, but in much less degree than in the neck. With dimi¬ 
nished angularity of the inferior keel, and the removal of the parapophysis from off the 
centrum, the contour of the articular ends of this becomes less shield-shaped and more 
rounded, until in the posterior dorsal region and in the loins it is approximately circular. 
The depression so marked in the sides of the cervical vertebrae below the neuro-central 
suture decreases in approaching the trunk, and from the mid-dorsal region to the 
loins the sides of the centrum are approximately flat in the vertical direction. In the 
longitudinal direction they are rendered slightly concave by an expansion of the 
centrum towards its ends. The transverse processes, in the anterior dorsal region 
stout and relatively long, have a capitular costal facet on their front edge where 
they spring from the neural arch, and a tubercular facet at their free end. Towards 
the loins the ■ capitular facet approaches the tubercular, and in the lumbar vertebrae 
the relatively short stout transverse process has only a terminal facet. The 
average length of the dorsal and lumbar centra in No. 39,460 Brit. Mus. Coll, is 
17 millims. ; that of the vertical diameter of the articular ends is 14 millims.; and 
that of the middle of the centrum is 12 millims. The three last lumbar vertebrae in a 
piece in my collection (No. 110) are each 20 millims. long. The terminal lumbar 
vertebra is distinguished from the others^by its greater bulk, and particularly by the 
enlargement of the posterior end of the centrum in adaptation to the corresponding 
surface of the first sacral with which it is often found anchylosed (Plates 75 and 76, 
fig. 2). 
Sacrum (Plate 74, fig. 9 ; Plates 75 and 76).—This comprises, as already stated, five 
vertebrae. These and the terminal lumbar in mature individuals are usually anchylosed 
together, with sometimes, but less frequently, I think, the first post-sacral vertebrae. 
All the five sacral vertebrae are smaller than the terminal lumbar. The first sacral is 
distinguished from the others by the great lateral expansion of the front end of its 
centrum (Plate 75, 1 s.). The shape of the second sacral centrum is cylindroid ; it is 
constricted at the middle and expanded at its ends, which makes the lower outline of 
the sacrum sinuous. The swelling that marks the junction of the anchylosed centra is 
not a uniformly tumid ring, but is greater where the inferior and lateral surfaces meet, 
forming here a pair of small knots, as in Iguanodon Mantelli. Interiorly, instead of 
being angulated through the inclination of the sides, as in I. Mantelli, the sacra] 
centra in Hypsilojphodon have a shallow median groove. The lower transverse pro¬ 
cesses are attached laterally at the junctions of the centra, they pass directly outwards, 
and their outer ends expanding antero-posteriorly coalesce and form a series of loops 
These are -well illustrated by the Plate referred to in the preceding page. 
