94 
FOSSIL REPTILIA OF THE 
laterally with the paroccipitals (PI. XXVI, fig. 1,4); but between these and the basisphe- 
noid it joins the mesially inclined hinder end of the pterygoids (ib., 24). The apex of 
the superoccipital (3) is wedged into the interspace of the hinder bifurcation of the parietal 
bones (7'), which it underlaps and partly supports ; its base forms the upper border of the 
foramen magnum. The paroccipitals (ib., 4, 4), broadest where they join the basioccipital, 
contract as they extend outward into a strong triedral bar, which abuts against the 
tympanic (28), at the interval between the mastoid (8) and pterygoid (24). 
The centrum (l), neurapophyses (2), neural spine (3), and parapophyses (4) of the 
hindmost cranial vertebra are instructively demonstrated by the Ichthyosaurian condition 
of the ‘ occipital bone ’ of Anthropotomy. 
The basisphenoid (PI. XXV, fig. 1, 5) presents, on its under and outer surface, the 
form of an irregular, subquadrate plate, narrowest behind, where it joins the basioccipital, 
expanding as it advances, the anterior border presenting a rough, sutural, notched 
surface, at its middle third, for the presphenoid (9), and a smooth emargination on each 
side forming the hind border of the sphenopterygoid or ‘ interpterygoid ’ vacuities ($, s)-^ 
The hinder half of the under surface of the basisphenoid presents shallow rough depres- 
sions and feeble risings for muscular attachments, and, like the basioccipital, it is 
imperforate. Of the alis])henoids I have been unable to determine more than their 
presence and their small size. The side walls of the brain-case proper seem to have been 
mainly cartilaginous. 
The parietals (7) in most Ichthyosaurian skulls retain their median (sagittal) suture 
(PL XXIII, fig. 1, 7), which usually opens out anteriorly to form the hind end of the 
' foramen parietale ’ or fronto-parietal fontanelle^ (/), the chief part, or whole, of which is 
bounded by the frontals (11). 
The upper surface of the parietals seems, by reason of the aspect of the occipital por- 
tion, to be divided by a ridge (>•) extending from the mastoids (8"), and continued upon 
the parietals to their mid-suture, into an anterior (7) and posterior (7') surface. This masto- 
parietal ridge (s" r) properly bounds, above, the occipital surface, to which the parietals 
thus contribute about a fifth part of their length above the superoccipital bone (PL XXVI, 
fig. 1, 7')- Anterior to this ridge each parietal slopes to the temporal fossa (PL XXIII, 
tig. 1, t), the parietal surface being divided by a low longitudinal rising continued forward 
from a posterior convexity into two facets, both of which are concave across. The dividing 
ridge is overlapped by a postero- mesial angle of the postfrontal (12), between which and the 
frontal a narrow; forward continuation (7") of the parietal is exposed, which overlaps the 
^ ‘Anatomy of Vertebrates,’ vol. i, p. 157, fig. 98, D, s. 
^ “This foramen, or ‘fontanelle,’ is common in the Triassic Reptilia. It is described and figured in 
Galesaurus, Fetrophryne, Dicynodon, Ptychognathus, Oudenodon, Kisticephalus, and Frocolophon ; in the 
latter it is large. It is wholly ‘ parietal ’ in Kisticephalus and Ftychognathus, in which it is placed far 
back.” — ‘Descriptive and Illustrated Catalogue of the Fossil Reptilia of South Africa in the British 
Museum,’ 4to, 1876. 
