1040 
PROFESSOR OWEN ON SOME REMAINS OF THE 
the diapophyses or “ paroccipitals ” to form strong triedral costal processes, more or 
less broken away, in the fossil (ib., figs. 1 and 2, 4 ). The lower surface of the basi- 
occipital is transversely convex at the middle part, concave on each side. 
The basisphenoid develops laterally a pair of hypapophyses in the form of low tube¬ 
rosities, for the attachment of strong “ recti capitis ” muscles ; on the left side the 
process shows a second pointed prominence. In advance of these are the bases of 
larger outstanding processes against which the pterygoids abut, in Moloch and other 
Lizards; these processes (ib., fig. 2, 5', 5') answer to the pterapophyses in the basi¬ 
sphenoid of Birds. At the anterior interspace of the above processes is the small 
surface (ib., fig. 2, 9) —here fractured—from which the presphenoidal rostrum was 
continued. Above the base of this process is the “sella turcica” (ib., fig. 2, 5), into 
which open a pair of vascular canals. The sides of the “sella” are produced into a 
pair of sub-compressed processes, as in Iguana (ib., fig. 4, 5). Megalania here differs, 
mainly, in the deeper excavation of the sella and the closer approximation of the 
vascular (entocaroticl) canals. 
The next difference is shown by the noil-articular termination of the pre-zygapophyses 
(ib., figs. 1 and 2, 5', 5 ) of the occipital vertebra, and also of its spinous process (ib., ns), 
which ends obtusely and freely, like the neural spine of a trunk-vertebra. 
The post-zygapophyses are those which are applied and anchylosed to the long and 
strong substrihedral paroccipitals (ib. 4), extending outward and backward from the 
sides of the centrum and neural arch of the occipital segment. The part extending 
from the sides of the centrum is much less than that from the neurapophyses, from 
which it is divided by the nerves issuing from the vagal foramina (ib., fig. 1, v, v), 
which pierce the base of the neural arch obliquely from within, outward, and back¬ 
ward, thus indicating the par- and di-apophysial constituents of the strong occipital 
transverse processes. 
In the trunk-vertebrae of Megalania the neurapophyses, as they rise to form the 
side walls of the neural canal, develop, as has been shown (Phil. Trans., 1858, p. 44, 
Plate 7, fig. 4, n), a ridge projecting inwardly from their medial surface about hall 
way between the floor and roof of the canal, the ridge beginning in advance of 
the hinder outlet. The exoccipitals repeat this neurapophysial character, but the 
encroaching ridges have greater basal extent and terminate obtusely, converting the 
anterior outlet of the occipital vertebra (Plate 36, fig 2, n') from a circular to a 
triangular or triradiate figure. The anterior outlet of the occipital neural (“ epen- 
cephalic ”) canal is similarly modified in Iguana, but with a minor prominence of the 
inner side-surface of the neurapophyses. Accordingly, the triradiate form of the front 
outlet is more marked in Megalania, and both vertical and transverse dimensions 
are relatively less than in Iguana, still less than in the more diminutive Moloch 
(ib. fig. 5). 
The more instructive part of the skull in advance of the occipital segment, in 
relation to the Lacertian affinities of Megalania, has come to hand in the present year. 
