CRETACEOUS FORMATIONS. 21 



Genus, Coniosaurus,* Owen. 



Species, Coniosaurus crassidens. (Tab. IX, figs. 13, 14, and 15.) 

 Dixon's ' Geology and Fossils of the Tertiary and Cretaceous Formations of Sussex,' 4to, p. 386. 



Two genera of Lizards of the Cretaceous period, with procoelian cup-and-ball 

 vertebrae, similar in size and form to those of the series figured and described in the 

 ' Geological Transactions,' vol. vi, 2d ser., pi. 39, fig. 3, are now no longer hypothetical, 

 but have been satisfactorily established by the discovery of portions of jaws and teeth 

 associated with such vertebrae. The first of these specimens, which discloses a small 

 extinct Lacertian,. distinct from Raphiosaurus, and characteristic of the chalk formation, 

 was obtained from the Middle Chalk at Clayton, Sussex, and forms part of the choice and 

 instructive collection of Henry Catt, Esq., of Brighton. It is figured in T. IX, figs. 14 

 and 15, and a group of vertebra? of apparently the same species is represented in fig. 13. 



These vertebrae are represented of the natural size. Like those first figured in the 

 ' Geological Transactions,' torn, cit., pi. 39, they present an anterior concavity or cup, 

 and a posterior ball upon the bodies for their reciprocal articulation ; and a tubercle is 

 developed from each side of the vertebral body near its anterior end, for the articulation 

 of the rib. The non-articular surface of the vertebra is smooth ; its under part is 

 concave in the axis of the body, convex transversely. On the very probable supposition, 

 however, that the vertebrae in fig. 14 belonged to the same animal as the jaw which 

 is imbedded in the same portion of chalk, such vertebrae must be smaller in proportion 

 to the head than in the extinct species of Lacertine Saurian, T. X, fig. 1, likewise from 

 the chalk, and to which there will be adduced reasons for believing that the fine speci- 

 men, in the collection of Sir P. de M. Grey Egerton, Bart. (ib. fig. 4), belongs. The 

 fossil jaw and teeth in fig. 14 determine the distinctness of the Coniosaurus from the 

 above-named fossil, as well as from all known recent Lizards. 



The dentary bone contains from eighteen to twenty teeth ; the anterior five or six 

 teeth are slender, slightly recurved, pointed, or laniariform ; the rest progressively 

 increase in thickness as they are placed further back ; expanding above the neck, 

 slightly compressed laterally, most convex inwardly, with an anterior border, which 

 is more prominent and curved than the posterior one : the anterior margin is further 

 characterised by a longitudinal groove on its outer side. Some of the posterior teeth 

 show a slight longitudinal indent near the posterior obtuse border ; the last molar is 

 smaller and more obtuse than the others. The enamel is very finely wrinkled. The 

 teeth are closely and rather obliquely arranged ; the long simple roots are anchylosed 

 to the bottom of the shallow alveolar groove, and to the inner side of the outer wall, 



* Kens, tos, chalk ; aavfjos, lizard. 



