DEVELOPMENT OF THE SKULL IN THE LACERTILIA. 
603 
From the side (fig. 3), the transpalatine and pterygoid are seen to be locked 
together, and from thence the pterygoid, having dipped to this point, rises in a concave 
manner up to the inside of the tympanic notch of the quadrate. 
Where the great basipterygoid. wings of the basi-sphenoid stand out, there the 
pterygoids carry a long, oval, cartilaginous facet, the counterpart of that on the cranial 
spur ( h.pg .), which gets slightly under the pterygoid (fig. 2 , pg., b.pg.). 
There is a patch of small teeth near the fore end of the pterygoid on its under face, 
overlapping the palatine articulation. 
The manner in which the pterygoids are bowed downwards is showed in the side 
view (fig. 3), and their outward curve, at the end, is shown in the end view (fig. 4). 
These three pairs of bones are properly endoskeletal, but are wanting in their 
cartilaginous correlates : the rest of the skull is either cartilage, or bone formed by 
the transformation of cartilage through the medium of deep ectosteal laminse, or 
imperfect bone—calcified tracts not perfectly changed into tracts of osteoblasts. 
The cranium proper is a remarkable structure (Plate 43, fig. 7), which would have 
been tolerably uniform if the middle pair of sense-capsules had not been free. They 
modify the cranium for room, pressing it inwards ; the other two pairs, nasal and audi¬ 
tory, are completely wrought into the general building. 
The hinder third is well ossified, the front part not at all, and the middle or orbital 
region imperfectly; dry skulls, such as are seen in Museums, hide more than they 
display. 
The occipital arch is ankylosed to the two hinder pairs of the “ periotic ” bones, 
the front pair (prootics, pro.) are permanently distinct, for the alisphenoids do not 
ossify as in the Snake and unite with these periotics ; yet the three, on each side, keep 
apart, even in the Snake. 
Along the mid line of the roof there is nothing but cartilage or membrane—the 
great upper fontanelle (fo.), up to the very edge of the occipital arch (Plate 42, fig. 4, 
aud Plate 43, fig. 7, so.), for the crown of that arch is a plate of cartilage. 
The middle part of the skull is a delicate basket of cartilage, only ossified here and 
there (Plate 43, figs. 2, 7, 8). 
All of a sudden, in front, the skull becomes a large swelling mass ; this is caused 
by the fusion, at the mid line, of the nasal capsules with the fore part of the axis. 
At its weakest point the cranium is propped up with a bony pole on each side 
(epg.) ; this, however, is a supernumerary element of the mandibular arch, the 
epipterygoid or “ columella” (not the same as the auditorg “columella,” which is the 
epihyal element fused with the stapes). 
The fusion of the exoccipitals (e.o.) with the opisthotics (op.) forms the sides of the 
arch and the large “parotic” or “ paroccipital” wings (Plate 42, fig. 4; Plate 43, 
fig. 7) ; these parts are characteristically Lacertilian. 
The broad tw r o-winged key-stone, like the sides of the doorway (foramen magnum, 
/to.), are seen to contain the canals of the labyrinth; each wing above was a separate 
