THE SKULL IN THE CHAMELEONS. 101 



5. The prefrontals articulate with the nasal process of the premaxiUary, in front of 

 and below the nasals. 



6. The nasals are very feebly developed, and fail to cover their own region, leaving 

 a membranous fenestra between themselves and the prefrontal, right and left. 



7. The premaxillary is a feeble edentulous wedge of bone, almost excluded from the 

 fore palate. 



8. The adult of the Dwarf and the young of the Common Chameleon have a normal 

 temporal space ; the postorbital and squamosal unite below, and form the lower 

 boundary, which is enclosed by the parietal above. In Lizards, generally, the parietal 

 forms the upper (inner) boundary of the large temporal space, which is bounded by the 

 postorbital and squamosal below or outside ; in many cases the supratemporal helps the 

 parietal "horn" to enclose this space above; but in Iguana tuherculata the supra- 

 temporal fits inside the horn. In the adult Common Chameleon the paired parietal, 

 being aborted in front and ankylosed to the top of the squamosal behind, helps to form 

 tlie lower or outer boundary of the temporal space, each inner being entirely formed by 

 the large individuated interparietal. In Lizards, generally, each parietal " horn," passing 

 outwards and backwards to the postero-external angle of the skull, forms a fost- 

 temporal space between the hind skull (occipito-auditory region) and itself In 

 " Cyclodonts " {Trachydosaitrus) the huge, arcuate, parietal horn comes so close, in 

 front, to the dilated postorbital, as almost to obliterate the temporal space ; for 

 above there is merely a small tract of membrane, which finishes the temporal roof. 

 Thus there is a great open space behind the horn, and this skull approximates to that 

 of the Green Turtle {Chelone viridis). In the Chameleon the two spaces (temporal and 

 posttemporal) are about equally divided by the parieto-squamosal bar (Plate XVI. 

 figs. 3 & 4), which rises over and spans this great tract, not seeming to divide it into 

 two distinct spaces, as in the Lizards, generally, where the posttemporal space is small 

 and lanceolate. 



9. The absence of a parasphenoid in the Common kind is a rare character; I have 

 only missed it, in other Lizards, in Trachydosaurus rugosus. 



10. The single vomer is very remarkable ; and this condition is not due to fusion of 

 the centres ; it is azygous in the embryo, as in the Chelonia. 



11. The absence of the septo-maxillaries is a correlate of the singleness of the vomer, 

 and of the peculiar position of the nasal glands, above and behind the nasal roof. 



12. I consider the intense fusion of the teeth with the jaw-bone, and the absence 

 oi pterygoid teeth, to be worth mentioning, as well as the absence of teeth on the pre- 

 maxillaiy. 



13. The peculiar depth and great size of the pterygoid behind, and its shortness, 

 ending in front of the quadrate, and united to it by ligament ; in the Lizards generally 

 the pterygoid is thin and falcate behind, and binds strongly inside the quadrate. 



VOL. XI. — PAKT III. No. 7. — March, 1881. r 



