LIASSIC FORMATIONS. 
29 
Lacertilia, to which ' neurapophysial ’ ridges (Tab. XIII, fig. 2, n, n ) may have been 
attached the neurapophyses, hut retaining, as in these Lacertilia, more or less of their 
primitive histological fibro-cartilaginous condition. The under and lateral parts of 
the mesencephalic centrum, called ‘ basisphenoid,’ are covered by the largely developed 
‘pterygoids^ (ib., fig. 1 , 24), — the diverging appendages of a more advanced cranial 
segment. The back part of the third or ‘ prosencephalic’ centrum has coalesced 
with the second, the boundary-line being indicated by a shallow depression, which 
may have lodged the vascular appendage of the brain called ‘ hypophysis,’ or 
‘ pituitary gland.’. The sides of this part of the centrum rise, neurapophysially, 
and terminate with a fractured and worn surface, and the rest of the centrum, 
answering to the cetacean ‘presphenoid’ ( 9 ), has been broken away. Beneath 
the fractured end of the presphenoid is the nasal ‘meatus,’ or canal (ib., fig. 1, r), 
which is divided below by the junction of the palatines (ib., fig. 2, 20, 20) with the 
pterygoids (ib., 24, 24), so as to open upon the roof of the mouth by a pair of posterior 
or palatal nostrils ‘ palatonares’ (ib., r,r)- These are of a narrow, elliptical form, with 
the long axis longitudinal, but slightly, inclined ‘ mesiad,’ or converging anteriorly, 
pointed behind, 1 inch 6 lines in long diameter, 7 lines across their widest part, and 
separated anteriorly by a tract of bone 9 lines across ; from the posterior end of the 
‘ palatonares’ to the same part of the basi-occipital tuberosity is I inch 5 lines. The 
palatines (ib., fig. 2 , 20, 20), where they give attachment to the pterygoids, are narrow, 
rather thick, with a shallow median channel, bounded by low, lateral, obtuse risings ; 
external to these the palatines form the anterior ends of the ‘ palatonares,’ and thence 
expanding, and flattening as they stretch forwards, they unite laterally with the 
ectopterygoids (25, 25). The pterygoids (24, 24), which form the inner and posterior 
boundaries of the palatonares, expand as they pass backward, become thinner and 
flatter, and retain a sutural union along the mesial line until they reach the precondy- 
loid fossa of the basi-occipital ; underlying and concealing from view, inferiorly, the 
basi-presphenoid and major part of the basi-occipital. These ‘ basilar’ plates are 
slightly concave from side to side, and are divided from the ‘ tympanic ’ pro- 
cesses (24', 24') by a rising of bone, hardly to be called a ridge ; this is chiefly formed 
by the concavity or sinking of the surface at the commencement of the under part of 
the ‘ tympanic’ process, which also gradually contracts in breadth as it extends 
backward and outward to abut against the tympanic pedicle (28), which is wedged at 
its upper or cranial half between the pterygoid (24) and par-occipital (3). 
The ectopterygoid (ib., fig. 2,25) articulates with the pterygoid near the posterior part 
of the palatal nostril, where it is about seven lines in breadth ; this joint has been put 
out by pressure on the right side and the ectopterygoid dislocated downward ; the 
corresponding part is broken off on the left side, where it overlaps the pterygoid, 
forming the outer boundary of the palatal nostril. The ectopterygoid expands as it 
advances forward ; curving, mesially, round the fore part of the nostril to join the 
