1R92.] 191 [Cope. 



except in Anniella and Chama^leon, where it is absent. The angular 

 bone never reaches the angle, and has an anterior position, being some- 

 times fused with the articular. The relations of the segments of the lower 

 jaw are very characteristic in the divisions of the Lacertilia. The splenial 

 bone is wanting in the Chama?leonida}, and is very small in the Agamidac ; 

 in other families it is well developed. 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, and not anteriorly, in the Chamajleonidaj and 

 AgamidiE ; both forwards and backwards in the Gecconidge ; and forwards 

 in the other families. The angular is absent (fused with the articular 

 Boulenger) in the Gecconidse, Anolidte, Acontiida?, Anelytropsidoe, 

 Anniellida^ and the Annulata, and is distinct in all other families. 

 The articular and surangular are fused in several genera of Iguanidne ; 

 and there are but three bones in the ramus of Xantusia, q. v. The angular 

 extends well anteriorly on tlie inferior border of the jaw in this order, but 

 is differently developed on the inner and outer faces. The ChamiBleonidse 

 and Agamida; again show their similarity in having this element chiefly 

 exposed on the interior side, while in other types the exposure is external. 

 The Meckelian groove is open in the Chamaeleonidse, Agamidaj and Va- 

 ranidse, but is roofed over more or less completely in all other families. 



The liyoid system is not connected with the skull except in Gecconidte, 

 Eublepharidaj and Lepidopbyma, so far as I have examined them. Thus 

 in Thecadactylus, Phyllodactylus and Eublepharis, the ceratohyal is con- 

 tinuous with a cartilage which projects from the paroccipital above the 

 posterior part of the auditory meatus. In Lepidophyma the free epi- 

 branchial is attached to the inferior lateral angle of the basioccipital. 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 carti- 

 lages. The hj^oid system in lizards consists of a glossohyal which is con- 

 tinuous with a basihyal tract ; a hypohyal often continuous with the 

 basihyal tract ; a ceratohyal ; a first ceratobranchial, and a second cerato- 

 branchial wliich 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 (Eumeces, Oligosoma, Gerrhonotus), or to 

 the second ceratobranchial (Lacerta, Xantusia, Lepidophyma). The only 

 constantly ossified element is the first ceratobranchial. The genera and 

 families difier in the presence or absence of the second ceratobranchials 

 and epibranchials ; and the proximitj- or separation of the former. In 

 general the Varanidte, Anguida?, Zonuridaj, Gerrhosauridse, Scincidaj, 

 Lacertidse and Xantusiidae have epibranchials, while the thick-tongued 

 and most degraded types are without them. In the Tiidoe the hypo- 

 branchials are much produced anteriorly beyond the bases of the cera- 

 tohyals, and there are no second ceratobranchials. In Anguidse the 



PROC. AMER.. PHILOS. SOC. XXX. 138. Y. PRINTED MAY 9, 1892. 



