92 ME. E. T. NEWTON ON A MEGALOSAUHOID JAW [Feb. 1 899, 



The resemblance which this jaw bears to the corresponding 

 parts of Megalosaurus is so striking that the reference of the fossil 

 to the same genus appears, at first sight, to be justifiable. A 

 nearer comparison, however, shows that the teeth of the present 

 specimen are less compressed and more curved than in Megalo- 

 saurus, besides being smaller than in any known species of that 

 genus. The vascular apertures of the outer surface appear to be 

 differently placed. Moreover Megalosaurus is essentially a Jurassic 

 genus, and although representative species have been found in 

 newer formations, even to the top of the Chalk, yet it has not been 

 recognized in beds older than the Inferior Oolite. The nearly-allied 

 North American genus Oeratosaurus is likewise of Jurassic age. 



Similarly serrated and compressed teeth have been found in 

 beds of Liassic, Eheetic, and Triassic age, but these have been 

 referred to other genera. 



It was Huxley,^ in his classical paper, who first definitely 

 established the occurrence of Dinosaurian reptiles in British Triassic 

 rocks ; but he was careful to point out that Eiley & Stutchbury ^ 

 had already noticed the resemblance which a large femur from 

 the Bristol Magnesian Conglomerate bore to that of Megalosaurus, 

 and that Owen^ had subsequently referred this femur to the 

 Dinosauria. 



The genera Thecodontosaurus and Palceosaurus, so named by 

 Eiley & Stutchbury from fossils found in Triassic conglomerate and 

 preserved in the British Museum (Nat. Hist.), were shown by Huxley 

 to be true Dinosaurs. The teeth of the former genus are leaf-shaped 

 and serrated, while those of the second are curved and lanceolate, 

 with the serrations of the anterior edge extending only a short distance 

 from the apex. The teeth of Palceosaurus resemble somewhat those 

 of Megalosaurus, but differ from them in being more cylindrical. 



Certain teeth from the Warwickshire Trias, now in the Museum 

 of Practical Geology, were also referred to Palceosaurus by Huxley, 

 and a larger tooth, much compressed and serrated throughout the 

 anterior and posterior margins, was placed in the genus Terato- 

 saurusJ^ This tooth is scarcely distinguishable from one belonging to 

 Megalo.saurus superhus of the Gaalt,' in which the serration of both 

 margins is coextensive with the tooth-crown. 



The characters by which Megalosaurus is distinguished from 

 Teratosaurus are seen in the vertebrae and limb-bones, and as these 

 parts of the skeleton were not found with the Warwickshire tooth, 

 Huxley was justified in referring it to the latter genus. Moreover, 

 Megalosaurian remains have not been recognized in Triassic beds. 



Mr. E. Lydekker ^ has pointed out the identity of Plieninger's 

 genus Zancloclon (1846) and Yon Meyer's genus Teratosaurus (1861), 



1 Quart. Joiirn. Geol. Soc. vol. xxvi (1870) pp. 32-50 & pi. iii. 



2 Trans. Geol. Soc. ser. 2, vol. v, pt. ii (1836) p. 349. 



3 ' Paleontology,' 2nd ed. p. 278. 

 * Huxley, oj-). cit. pL iii, fig. 11. 



® Gaudry, •Enchainem. du Monde Anim. : Foss. Second.' 1890, p. 222. 

 « Oat. Foss. Eept. Brit, Mas. pt. i (1888) p. 172. 



