78 PEOF. W. K. PARKER ON THE STRUCTURE OF 



shoulder-girdle and sternum ("Shoulder-girdle and Sternum," plate xi. figs. 4-6, 

 p. 122); and I have no doubt that every part of its organization, if well worked out, 

 would show some very important modifications. 



But in the culminating types of any group whatever, some archaic characters are sure 

 to crop up. I find this " survival" in the Frog among the Anura, and in the Nimble and 

 Green Lizards among the Lacertilia : in the former, which is the best pattern-form for the 

 group, there are two or three characters that are exceptional ; and in the latter, the 

 most refined and delicate forms in the Lizard group, the whole cranial roof, from snout 

 to occiput, might have been directly, and not remotely, derived from some most ancient 

 Ganoid fish (see "On the Skull of the Lacertilia," Phil. Trans. 1879, part ii. plate 42, 

 p. 597). 



Skull of the Adult Chameleon {Chamceleo vulgaris). 



Seen from above, or below, the outline of this skull is a long oval ; from the side it is 

 seen to have a short, steep face, almost as steep and short as that of a Tortoise, and to 

 be surmounted behind by an exorbitant three-limbed crest ; it has huge eye-sockets, and 

 a steep hinder region. 



In this species, and still more in other larger and more bizarre kinds, the marginal 

 bones of the skull-roof are very large, crested, and adorned with knobs and prickles, 

 as though it were showing a tielacliiaii atavism, and had compounded its investing 

 bones out of the shagreen jjrickles and the ossified skin of some such Placoid forefather. 



The roof dips ; and the frontal is not seen from the side ; and the w hole upper outline, 

 looked at from above (Plate XVI. fig. 3), is like the plan of a double arch, with the coronal 

 suture as a common basal line. But the keystone in front, the single premaxillary {px), 

 is wedged in between the fore face below and the fore skull above. The hinder key- 

 stone, the interparietal [i.])), binds and finishes the arch that springs from the great 

 auditory wings (Plate XVI. fig. 4). The lower edge of the fore part of the skull 

 spreads out into a much broader structure than the upper ; its margins are the maxil- 

 laries {mx) ; the upper outline of the fore part is formed by the prefrontals {p-f) (super- 

 ficial or dermal ethmoids). The middle of the upper margin is formed by the post- 

 orbitals {ft.o) ; and the form is finished behind by a pair of compoimd bones, the 

 squamoso-parietals {sq.j}.). Thus the single adult frontal (/') is completely enclosed, 

 and forms the centre of the somewhat sunken roof, which is finished behind by the base 

 of the huge crested interparietal {i.p). 



The lower surface shows a broad latticework, very complex, and very compound ; it 

 is composed of subcutaneous plates and of submucous bones (that are ectostoses in lower 

 types), of cartilage, and of cartilage-bones ; for in this view we see the basis cranii, 

 the complex palate, and the marginal bones of the face. The side view (fig. 1) shows 

 the steepness of the face, the height of the crest behind, the strength of the fiat jaws. 



