THE SKULL IN THE CHAMELEONS. 79 



the depth of the mandibular pier, and the size of the eye-sockets, with their mem- 

 brano-cartilaginous partition. 



The end view (fig. 4) shows an almost vertical structure, semioval in shape, whicli is 

 the frame of a S3'stem of openings or archways. In the centre we see the foramen 

 magnum (y.m) on each side ; above, the huge temporal openings ; directly below, the arch- 

 way under the skull and between the steep pterygoids (pg) ; and outside those bones a 

 steep oblique space, whose outer boundary is the high \eitical quadrate or mandibular 

 pier; this outer space, on each side, is again subdivided by the transit of the long 

 descending columella auris. 



A. The Investing Bones. 



This remarkable building must now be taken to pieces (ideally), and described part 

 by part. 



The frontals (f) are completely fused together, and form a broad plate over the fore 

 part of the cranial cavity. The coronal suture is nearly transverse ; and in front of it, 

 contrary to rule, in a hollow surrounded by tubercles, we see the round fontanelle (fo). 

 Each side of the bone is cut away in a concave manner four times ; and the fore part is 

 a sharp spike wedged in between the nasals. 



Those bones (w) are small and falciform, witli their sharp ends, behind, binding on the 

 last shallow pair of notclies on the frontal. In front a sharp spike of bone, the nasal 

 process of the premaxillary (n.jn-), wedges in between these broad ends, and almost 

 touches the frontal wedge. 



The margins are formed above, half by the prefrontals (p-f) and half by the so-called 

 postfrontals (" postorbitals" p)t-o). Each prefrontal is an irregular plate of bone, high- 

 crested and arched ; it encircles the front third of the huge orbit, and runs inwards as an 

 anteorbital plate behind the nasal capsule. Above, it articulates by sutures with two of 

 the shallow notches of the frontal ; it is then itself notched in a crescentic manner, 

 leaving an oval membranous space between it and the narrow part of the corresponding 

 nasal ; its narrowed fore part binds, first upon the broad end of the nasal, and then upon 

 the nasal process of the premaxillary. In front (fig. 1) it reaches down to articulate 

 with the maxillary (mx) above the nasal opening (al. n, e. n) ; and behind it articulates 

 with the postorbital {pt.o) over the middle of the orbit. The suture at this part is 

 jagged or dentate ; and both the bones being narrowed where they meet, a triangular 

 part of the frontal (/) appears in the roof of the orbit. 



The fenestra between the nasal and prefrontal {n.,p.f) is directly over the continuous 

 aliseptal roof; here the fenestra is in the bony investment; in Lacerta that roof is 

 complete, but the cartilaginous capsule is imperfect, there being a nasal fenestra in the 

 proximal part of the aliseptal cartilage on each side (" Skull of Lacertilia," part i. Phil. 

 Trans. 1879, pi. xliii. fig. 7, p. 607). The next bone, the postorbital {pt.o), has its fore 

 half binding against the roof (/, i.p), and its hinder half projecting outside and beyond it, 



o2 



