CROCODILIANS, LIZARDS, AND SNAKES. 189 



augular extends well smteriorly ou the interior border of the jaw in this 

 order, but is diftereutly developed ou the inner and outer faces. The 

 Chanmeleonidte and Agamidic again show their similarity in having this 

 element chiefly exposed ou the interior side, while in other types the 

 exposure is external. The Meckeliau groove is open iu the Chamio- 

 leonidne, Agamidiie, and Varanidie, but is roofed over more or less com- 

 pletely in all other families. 



The hyoid system is not connected with the skull except in G-eckonidse, 

 Eublepharida^, and Lepidophyma, so far as I have examined them. 

 Thus in Thecadactylus, Phyllodactylus, and Euhlepliaris the ceratohyal 

 is continuous with a cartilage which projects from the paroccipital 

 above the posterior part of the auditory meatus. In Lepidopliynia the 

 free epibranchial is attached to the inferior lateral angle of the basioc- 

 cipital. In forty-two genera of other families enumerated below this 

 is not the case. In no genus have I discovered any connection with 

 the stapedial cartilages. The hyoid system in lizards consists of a 

 glossohyal which is continuous with a basihyal tract, a hypohyal 

 often continuous with the basihyal tract, a ceratohyal, a lirst cerato- 

 branchial, and a second ceratobranchial which is always continuous 

 with the basihyal tract. There may be in addition an epibranchial, which 

 belongs to the first ceratobranchial. In some genera there is a free 

 epibranchial, which may be then closely approximated to the ceratohyal 

 {Eiimeces, Oligosoma, Gerrhonotus), or to the second ceratobranchial 

 [Lacerta, Xantusia, Lepidophyma). The only constantly ossified ele- 

 ment is the first ceratobranchial. The genera and families differ in the 

 presence or absence of the second ceratobranchials and epibranchials, 

 and the proximity or separation of the former. In general the Varanida?, 

 Anguida', Zonurid<e, Gerrhosaurida^, Scincida^, Lacertida^, and Xantu- 

 siidai have ei)ibranchials, while the thick-tongued and most degraded 

 types are without them. In the Teiid* the hypobranchials are nuich 

 produced anteriorly beyond the bases of the ceratohyals, and there 

 are no second ceratobranchials. In Anguidse the hypobranchials are 

 also greatly produced forward, but carry the ceratohyals with them. 

 Ceratobranchials of the second pair are also wanting in Varanid;e, 

 Ilelodermida', Chama^leonida^, Anguida), Anniellida^, and Rhineiira; 

 PhyUodaetylus, Thecadactylus, and Geclio, among Geckoni;e; and ^^er- 

 nia, and Gongylus in Sclncidse. Ceratohyals are wanting in Chamwleon, 

 A)i()uis, Anniella, and Annulata generally. In both Agamidie and 

 Iguanida) the second ceratobranchials are separated from each other 

 iu the depressed genera of terrestrial habits, and in close contact with 

 oach other in those of arboreal habits; but they are in close contact in 

 CaUisaurus and Grotapliytus, both terrestrial genera. In Calotes, 

 fguana, and Anolis they act as the rim on which the gular pouch or 

 fan is stretched. The characters of Saurian hyoids may be tabulated 

 as follows : Most of the genera referred to are figured in Plates 111 

 to VI. 



