THE SKULL IN THE CHAMELEONS. 95 
of the U-shaped basioccipital. The hinder margin of the basisphenoid is lunate, 
not semielliptical, like the fore margin of the basioccipital ; its axial length is only half 
as great as that of the hinder bone. The basisphenoid would be a triangular wedge 
(for it ends in an almost pointed process in front); but it gives off at the middle on each 
side a wing of bone, dilated and cartilaginous externally. These wings are the basi- 
pterygoid processes (b.pq), whose direction is downwards, outwards, and forwards. 
The openings for the trigeminal nerves (Vv) are surrounded by membrane everywhere 
except a small tract below and behind; for here, in the alisphenoidal region, the mem- 
branocranium (a/.s. f) extends over the highest part of the head, and down on each side 
to the base (fig. 7). The alisphenoid (a/.s) is a feeble sigmoid bar in front of this space ; 
itis continuous with the basal cartilage, between the optic passage and the foramen ovale 
(u, V), and with the orbito-sphenoid (0.8) above the common optic passage. The lower 
half is ossifying, and is arched backwards; the upper half, which only reaches up to the 
most tumid part of the membranocranium, is soft, and bends forwards. Between this 
feeble rudiment of the “ala magna” and the orbito-sphenoidal lamina there is a deepish 
triangular notch. 
The chondrocranium in front of the ali- and basisphenoid is quite unossified ; in front 
of the great common optic passage (11) there is an oblique presphenoidal band (p.s) run- 
ning downwards and forwards to the trabecular base. In front of this there is a large 
oblong interorbital fenestra (7.0. J), not notch, as in Lacerta. 
The thick trabecular base below and the thin lamina above this fenestra are about 
equal in depth. From the upper part there proceed a pair of narrow orbito-sphenoidal 
wings (0.8); these soon become almost obsolete, and then widen in the ethmoidal 
region, where they are pierced by the olfactory nerves (1) and lie over the orbito-nasals 
(v1). The perpendicular ethmoid becomes a low middle wall, passing into the septum 
nasi (figs. 7 & 8), which divides the flat, but tumid, 4-celled nasal labyrinth, with its 
annular outworks (a/.sp, al.n). From the postero-inferior face of the capsule there is a 
small semioval cartilage projecting ; this is the ethmo-palatine (e.pa) 
Lhe Postoral Arches in the Young Chameleon. 
The whole articular head (otic process) and the pedicle and the base of the quadrate is 
still soft (fig 1, ot.p, pd, g. c); and part of the free mandible is unossified nearly to the con- 
dyle, not being covered, as yet, by the articulare (fig. 6, mk, ar). The long glosso- or 
basihyal rod, with its small terminal segment (fig. 8, ¢.dr, d.hy, b.hy'), is unossified ; also 
the ceratohyals (¢.hy) and hypohyals (A.hy). The thyrohyals, or 1st cerato-branchials 
(c.br), are well ossified already. as 
The long azygous rod is not quite so long, relatively, as in the adult ; it only reaches, 
if measured by the basis cranii, from the occipital condyle to the middle of the septum 
nasi. Q2 
