THE SKULL IN THE CHAMELEONS. 91 
cartilage passes upwards as a short suprastapedial (s.st); this is finished above by an 
enlarging ligament, which is inserted in the inner face of the quadrate, close to the top. 
The ceratohyals (Plate XVI. fig. 6, ey) are long, slender, sigmoid cartilages, end 
in a point above, and are attached by ligament to the skull; they are scarcely as large as 
the columella. The hypohyals (h.hy) are segmented off from the ceratohyals, are one 
third as long, one third thicker, and ossified, except at their extremities. These arti- 
culate by their narrow end with the basal piece at the fore part of its cartilaginous end, 
which grows backwards as an unsegmented basibranchial (6.6r). ‘The main rod, or 
basihyal, is as long as the whole basicranial axis of the same individual—from the end 
of the snout to the occipital hinge. Its fore end, for one eighth of its length, is unos- 
sified and segmented off (4.hy") ; the rest is a very even cylinder of bone, nearly as thick as 
the “ waist” of the quadrate ; it becomes somewhat slenderer in front. Loosely attached 
to the basibranchial end of the median piece are two arcuate ossified rods, bulbous at 
their soft end below, and rounded at their smaller upper end; they are the cerato- 
branchials (¢.4r) (thyrohyals); they are as long as, but thicker than, the ceratohyals, 
SKULL OF A NEWLY-HATCHED CuAMELnon (Chameleo vulgaris). 
(Total length 13 inch, head { inch, head and body ? inch, tail ? inch.) 
This skull is the counterpart of that of Zootoca vivipara, described in my paper on 
the skull of the “ Lacertilia” (Phil. Trans. 1879, plate 41, pp. 630-634) ; the length 
of those young lizards was nearly the same as that of the young Chameleon, viz. 13 inch. 
I shall throughout this part of my description compare these two skulls together. 
That which strikes the eye at first in the skull of the young Chameleon is its likeness 
to the skull of a young Mammal; for now the cranial cavity is very large and swelling, 
and contains a relatively large brain. 
The Investing Bones of the Young Chameleon’s Skull. 
I know of no skull whatever in which the roof-bones undergo so great a transforma- 
tion as in this. The single frontal of the adult is seen to have two rudiments in 
the young (Plate XV. fig. 3, f/); these are, even now, mainly in front of the cranial 
cavity, which becomes very narrow over the orbito-sphenoidal region. Thus only 
one third of each bone lies over the actual cavity, which contains the fore end of the 
hemispheres and the olfactory bulbs; the rest is due to the size, at this time, of the 
orbital rim ; this is a large lunate tract, convex above and concave below. 
Each frontal bone (fig. 3, f) is notched in front; the inner spike bounding the notch 
is longer than the outer, and runs up to the nasals and nasal process of the azygous 
premaxillary (n,n. px). The outer spike of the frontal runs, for a short distance, between 
the prefrontal and the nasal roof (a/.sp). The supracranial part of each bone dips to 
