188 REPORT OF NATIONAL MUSEUM, 1898. 



petrosal), Iguana,, Uromastix, Agama. aud Gonyocephahis {stibcristatus). 

 Ill Lyriocephalus and Phrynocephahis tlie epipterygoid is very short. 



The semicircular canals perforate the supraoccipital, the exoccipltal, 

 and the petrosal. The internal is in a subtransverse vertical plane, 

 causing a convexity on the internal side of the supra- and exoccipitals, 

 and in some types a visible rib on the superoexterual suface of the 

 same. The external canal is in a horizontal i)lane and perforates the 

 base of the exoccipitopetrosal suspensorium, causing a horizontal rib 

 on the anterior face of the latter in some forms. The anterior is in a. 

 vertical anteroi^osterior plane, and perforates principally the petrosal, 

 occupying its anterior border, which forms the " arcade" in most of the 

 thick- tongued superorders, but crossing the bono much behind the 

 anterior border in the slender- tongued superorders and the Diploglossa. 

 The fenestra ovalis is tightly closed by the disk of the stapes, which is 

 continued externally as the rodlike columella. This rod is slender 

 except in Anniella^wheTe it is remarkably robust. In the other AmphiS' 

 btenia its tympanic extremity is somewhat thickened. The columella 

 is continued externally into a cartilage,which is more or less expanded 

 in the vertico-transverse plane, the distal portion always so, forming a 

 vertical lamina in contact with the tympanic membrane. This is the 

 epistapedial cartilage. It is frequently produced upward beyond its 

 point of attachment into a suprastapedial process. The plate thus 

 formed is almost separate from the proximal axial part of the cartilage 

 in Heloderma} The axial portion has a descending process, the infra- 

 stapedial of Parker, in Lacerta, Seloderma, but not in Uuhlepharis, 

 Thecadactylus, and Phyllodactylus. 



The rami of the lower jaw are united at the symphysis by ligament 

 only. The angle is a prolongation of the articular bone; it is elongate 

 and siini)le, except in Anniella and Ghamceleon, where it is absent. 

 The angular bone never reaches the angle, and has an anterior posi- 

 tion, being sometimes fused with the articular. The relations of the 

 segments of the lower jaw are very characteristic in the divisions of 

 the Sauria. The splenial bone is wanting in the Chamiiileonidre, 

 and is very small in the Agamidie; in other families it is well devel- 

 oped. The dentary extends posteriorly on the external face of the 

 ramus, as the splenial diminishes, having the greatest posterior extent 

 in the two families mentioned. The coronoid is differently extended in 

 a similar ratio. Thus it is extended posteriorly on the external side of 

 the ramus, aud not anteriorly, in the Chamieleonidne and Agamidte; 

 both forward and backward in the Geckonida^; and forward in the 

 other families. The angular is absent (fused with the articular, Bou- 

 lenger) in the Geckonid;e, Auolidic, AcoiitiidiB, Anelytropsida', Anniel- 

 lidse, and the Annulata, and is distinct in all other families. The 

 articular and suraiigular are fused in several genera of Iguanidoij and 

 there are but three bones in the ramus of Xantusiaj which see. The 



1 Memoirs, National Academy of Sciences, III, 1884. 



