THE SKULL IN THE CHAMELEOXS. 91 



cartilage passes upwards as a short suprastapedial (sM) ; 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, c.hi/) 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.Jii/) 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 (b.br). 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 o^{h.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 {c.br) (thyrohyals) ; they are as long as, but thicker than, the ceratohyals. 



Skull of a newlt-hatohed Chameleon (Chamwleo vulgaris). 

 (Total length IJ inch, head ^ inch, head and body | inch, tail | inch.) 



This skull is the counterpart of that of Zootoca vivipara, described in my jjaper 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. 1^ inch. 

 I shall throughout this part of my description compare these two skulls together. 



That which strikes the eye at first in the skuU 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 SkuU. 



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. ?>,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,y) 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.])x). The outer spike of the frontal runs, for a short distance, between 

 the prefrontal and the nasal roof {aLsp). The supracranial part of each bone dips to 



