THE SKULL IN THE CHAMELEONS. 85 



wings (o.s) are seen to be only one third as wide behind as the alisphenoids (al.s) ; they 

 become only half their hinder width, and then expand again as they pass into the ali- 

 ethmoidal laminaj (a/.e), where the /oor of the skull passes into the roof of the nasal 

 pouches. 



Near each other, in the middle of tliis rewidened tract, the small oblique olfactory 

 passages i are seen; and further forwards, under these wings, the orbito-nasal nerves 

 (figs. 3 & 4, V') enter the nasal labyrinth. Where the middle ethmoid passes into the 

 septum nasi (Plate XVII. fig. 1, p.e, s. n), there is no " cranio-facial fenestra," as in 

 Zacerta (op. cit. pi. 43. figs. 1 & 2, c.f.f )^nd Trachjjdosaurus, but, as in the Struthionids 

 among Birds, the orbito-nasal partition is continuous, except in the presphenoidal 

 region. 



The valley over the ethmoidal wings has no ascending (tegminal) bar of cartilage 

 growing over it either here or in Lacerta ; but all Birds show a spike-shaped remnant 

 of the front cranial roof of the " Ichthyopsida " mounting over the channel for the 

 olfactory nerves. The endocranial roof, however, is very large behind in the Cliameleon, 

 as I have just shown. 



The nasal labyrinth, as seen from above (Plate XVII. fig. 4), looks like a quadricellular 

 capsule. It has four nearly equalswellings: the hinder pair are circular; and the front pair 

 have a helicoid appearance. The postero-lateral edge, in front of the ali-ethmoidal laminee 

 (al.e) is sinuously notched ; and in the notch are packed, right and left, the nasal 

 glands («.y). This is the position of these glands in certain birds where they are 

 moderately developed, as the Ehea and Fowl (Phil. Trans. 1866, pi. 9. fig. 5, n. (/, and 

 1869, pi. 86. fig. 9, H. r/). In Snakes and most Lizards, where the vomers are distinct, 

 these glands lie in the vomers as in a dish, and are covered by a lid-like bone— the 

 septo-maxillary (Phil. Trans. 1878, pi. 33, and 1879, pi. 42. v, n. g, s.mx). 



Here, in the Chameleon, the high (supero-posteriorj position of these glands is the 

 correlate (as in the Fowl), of a single vomer, and of suppression of the septo-maxillaries. 

 There is no more than a broad lip-like prenasal cartilage (Plate XVII. figs. 1, 3,& 4, 

 p.n), slightly bent downwards in front. Outside, in front, the outer nostrils (e. n) are 

 nearly encircled by a confluent labial {al.n) or alinasal cartilage, nearly closed above, and 

 very similar to the cartilaginous " annulus tympanicus " of the Frog. In the anteorbital 

 region the nasal labyrinth is complicated by an ethmo-palatine cartilage (Plate XVII. 

 fig. 3, and Plate XVIII. figs. 6 & 6.\, e.pa). 



Endocranium as seen in transverse sections. 



Here the various sections throw a welcome light upon the structure of the nasal 

 labyrinth (Plate XVII. fig. 2, and Plate XVIII. figs. 2-6a). 



In the side view of the septum nasi the cartilage is seen to be thickened at the ends 

 and middle of the septum; and the part removed to expose this structure (Plate XVII. 

 tig. 2) shows that the pouch on each side is subdivided into two, and that each of these 



VOL. XI. — PAET III. No. 5. — March, 1881. p 



