CRETACEOUS LIZARDS. 185 



mutilated body of a vertebra of these dimensions, together with the two caudal ver- 

 tebra% form part of that collection which was sold by Dr. Mantell to the British 

 Museum. No proof is given that these vertebrae belong to the same species as the 

 Mosasaurus Hojfmanni: the dorsal vertebra; of the great Mosasaurus of Maestricht are 

 more than double the size of the one above cited, which, in tlie complete anchylosis of 

 the neural arch, would seem to have belonged to a mature individual of that cold- 

 blooded genus. 



Subsequent discoveries of Mosasaurian Fossils in the English cretaceous deposits 

 have enabled the comparison with the specific characters of the Monamurus of Maes- 

 tricht, and of that from the Green sand of North America, to be carried out satis- 

 factorily, especially in reference to the modifications of the teeth. 



Mosasaurus gracilis, Owen. Lacerfians, Plate 1, figs. 1, 2, and .3. PI. 2, figs. 



I, 2, 3, 4, and 5. PI. 9, figs. 7, 8, and 9. 

 Dixou's 'Geology and Fossils of the Tertiary and Cretaceou.s Deposits of Sussex.' T. XXXIX. 



CuviER,* in his account of the great J/osascafr/fS of Maestricht, which is entered 

 in the catalogues of M. v. IMeyer and M. Pictet, under the synonyms JL C(nn])cri 

 and M. Hoffmaiun, states that "all the teeth are pyramidal, a little curved, with their 

 external surface flat (' plane') and divided by two sharp ridges from the internal surface, 

 which is round or rather semi-conical." Messrs. Von Meyerf and Pictet]: re})eat 

 Cuvier's description of the external characters of the crowns of the teeth ; the one 

 says, "ihre Aussenseite ist cben" — their outer side is flat or level; tlie other, "leur 

 face externe est plane." My description'^ of the tcetli of the Maestricht Mosasaurus. in 

 which it is stated that " their outer side is nearly plane, or slightly convex," was founded 

 on an examination of the magnificent fossil skull in the Parisian ^Museum, the original of 

 Cuvier's description ; — and the contour of the base of the crown of a maxillary tooth 

 of the Jlomsa/fr/f.s Iloffmanin given m PI. 10, fig. 7, is taken by accurate admeasurement 

 from a perfect specimen from the Maestricht chalk : the enamelled crown of this tootli 

 was two inches (five centimeters) in length ; the rest of the tooth was formed I)v the 

 enlarged coarse osseous fang; the total length of the tooth being four inches ten lines 

 (twelve centimeters and a half). Dr. A. Goldfuss, in his highly interestiniiand instruc- 

 tive description!! of the skull and teeth of the Jfosasaurits Ma.i'i/iiiliani, .accurately 

 describes and figures the finely dentated character of the two oj)posite longitudinal 

 ridges of the crown ; but the feeble indications of angles observaljle in some of the 



* Annates. Ju Museum d'Hist. Nat., xii, IMOS. Osscniens I'ossiles, ^to, v, pt. ii, p. .i'ii. 

 t Pahi'ologica, p. 21!). X Traite ek-mcntaire de I'aK'ontologie, ii, ]). (i.'i. 



§ Odontography, 4ti), p. 258. Nova .\cta .\ead. Nat. Cur., I. x.\i, p. 17.">. 



