290 RHYNCHOCEPHAUA. 



Varanus. Mandibular ramus very deep. The best preserved speci- 

 mens are figured by Owen in his ' Cretaceous Reptilia ' (lion. Pal. 

 Soc), pt. i. pi. ix. figs. 13-15. 

 Hob. Europe (England). 



25790. Fragment of the dentary bone of the mandible, with teeth ; 



from the Chalk of Washington, near Worthing, Sussex 



Mentioned by Owen in Dixon's * Geology of Sussex,' p. 388. 



Dixon Collection. Purchased, 1851. 



R. 62. Fragment of a dentary bone, showing four teeth ; from the 

 Chalk of Hart Hill, Charing, Kent. Purchased^ 1881. 



Order RHYNCHOCEPHALIA. 



Body and limbs usually more or less lacertiform. Proximal end 

 of quadrate immovably fixed ; inferior temporal arcade present ; 

 postorbital, at least in existing genus, distinct from postfrontal ; 

 palate closed ; and premaxillae separate. Vertebrae usually amphi- 

 coelous, but occasionally opisthoccelous, and sometimes with persistent 

 neurocentral suture ; no zygosphenes ; intercentra in some cases 

 present. Uncinate processes to ribs in some forms ; abdominal ribs 

 present. In the existing genus at least two centralia in carpus ; and 

 no distinct precoracoid. 



This order includes Reptiles with more or less generalized affini- 

 ties, in regard to the serial position of which very different views 

 obtain. By Cope l the group is placed between the Sauropterygia 

 and Chelonia, while by Huxley 2 it is included in the Squamata 

 (Lacertilia). The middle course proposed by Baur 3 , of regarding 

 these forms as constituting a distinct order, which is placed next the 

 latter, is here provisionally followed. 



Suborder HOMCEOSAURIA. 



Prcmaxilla3 apparently not forming a beak. Ribs without unci- 

 nate processes. Palatal dentition unknown. Tho group is referred 

 to this order by Baur 4 , who quotes the authority of Ammon 5 as to 

 the existence of an inferior temporal arcade, and suggests that inter- 

 centra were present. 



1 See Baur, Journ. Morphol. vol. i. pp. 93-99 (1887). 



2 Quart. Journ. Geol. Soc. vol. xliii. p. 692 (1887). 



3 Op. cit. pp. 99-100. 4 hoc. cit. 



5 Abh. k.-bay. Ak. Wiss. vol. xv. pp. 500-528, pis. i., ii. (1885). 



