ANATOMY OF VERTEBRATES. 155 



serrated by a single row of anchylosed teeth. The coronoid piece 

 is triangular, rises into a point, and presents a smooth articular 

 surface on its inner side, adapted to the anterior lateral projection 

 of the pterygoid. 



In the skull of the black Scink ( Cyclodus nic/cr-), the frontal and 

 parietal bones are thick and expanded ; the parietal is bifurcated 

 behind, and articulated with the mastoids and paroccipitals. The 

 postfrontals are separated from the malars by the squamosals, 

 which extend between the malars and the mastoids to form the 

 strong lateral bony arch resting anteriorly upon the malar and the 

 maxillary, and posteriorly on the parietal and tympanic. Con- 

 comitantly with the strong osseous roof of the cranium, there is 

 an arrest of osseous developement in the fibro-membranous 

 neurapophysial walls of the cranium : two lateral processes 

 extend downward into these walls from the parietal and for- 

 ward from the exoccipitals ; but the protective office of the 

 alisphenoids is solely performed by the columnar { columellas,' 

 which extend from the interspaces of the processes above 

 mentioned, to rest upon the upper groove of the pterygoids. 

 The orbitosphenoids are represented by still more slender bony 

 styles, which circumscribe the outlets for the optic nerves, and 

 form the anterior boundary of the prosencephalic division of the 

 cranium. The lacrymal bones are large and divided on each side, 

 as in most Lizards. The premaxillaries are confluent, and their 

 nasal process separates the external nostrils from each other. 

 Each pterygoid presents a rough surface towards the palate, but 

 does not support teeth. There is a small ossicle between the 

 pterygoid processes of the sphenoid and the true pterygoid bones. 

 The columelliform stapes is extremely long and slender. 



In the Iguana the parietal supports a single median crest : the 

 posterior margin of the frontal is notched by the fronto-parietal 

 fontanelle : both lacrymal and postfrontal are subdivided into two 

 pieces ; the lacrymal foramen is a e conjugational ' one between the 

 two pieces. The upper portion of the lacrymal represents the 

 facial part of the prefrontal ; it does not send down a neurapo- 

 physial plate to join the vomer or palatines, nor forms any part of 

 the lateral walls of the rhinencephalic cavity, or of the foramen 

 for the transmission of the olfactory nerves. The palatine nostrils, 

 fig. 98, D, n, are very long, and notch the large palatines, 20; the 

 pterygoids, 24, each support a row of small teeth. 



In the skull of the Monitor Lizard ( Varanus niloticus) the 

 basioccipital sends down a pair of short, obtuse hypapophyses : 

 those of the basisphenoid are larger and abut against the ptery- 



