THE KEPTILIAN CLASS OF THE MOSASAURIDJ3. 715 



" that they possess more affinity to the serpents than does any other 

 order "*. 



To this I respond that the fossil evidences of the Mosasanrians 

 hitherto made known do not yield a single character peculiar to and 

 characteristic of the Ophidian order. 



In the single occipital condyle and the composite structure of the 

 mandible the Mosasaurians are Reptilian ; in the procoelian vertebrae 

 they accord with the existing representatives of the class ; in the 

 double occipital hypapophyses, in the bifurcate and perforate parietal, 

 in the columella, in the composite formation of the suspensory joint 

 of the tympanic, in the type of the tympanic, in the frame of the 

 parial nostrils, in the composition of the mandible, and in the 

 structure and attachment of the teeth they are Lacertian ; in one 

 special dental modification they are Iguanian ; in another they are 

 Monitorial. In the broad cemental basis of the enamelled tooth, 

 in the more extensive fixation of the pterygoids and ossification of 

 the roof of the mouth, in the large proportion of the vertebral 

 column devoid of zygapophyses, in the confluence of the haemal 

 arch with the centrum of certain of the caudal vertebrae, in the 

 natatory character of the fore and hind limbs they are — what they 

 are — viz. Mosasaurian. 



Are they entitled, through the last category of modifications, to 

 the rank of an order in the reptilian class ? 



The order Lacertilia, in the class Reptilia, is a taxonomic equiva- 

 lent of the order Carnivora or Ferae in the mammalian class. 



In the Ferae there is a group which, by modifications of the 

 skull, teeth, vertebras, and, especially, limbs, takes rank as a suborder 

 or subordinate group, viz. the Pinnipedia or Phocidae. I estimate 

 the Mosasaurians in the Lacertian order to be equivalent to the 

 Seals in the Ferine order : and I concur with the judicious and ex- 

 perienced palaeontologist Paul Gervais in correlating his group 

 Mosasauridoe, in the Lacertian order, as to taxonomic value, with 

 his Iguanodontidae and Megalosauridae in the Dinosaurian order f . 



In conclusion, I may confess that I should hardly have been 

 moved to trouble the Society with facts so familiar to my palaeon to- 

 logical colleagues had it not been for a stray reference to " Pythono- 

 moypha " in the excellent " Address " to which we listened at the 

 last Anniversary with s.o much pleasure, from our esteemed and 

 accomplished President. 



* Op. tit. p. 126. 



t "Ces genres et plusieurs autres qui Ten rapprochent, paraissent constituer 

 trois families distinctes, toutes absolument etrangeres aux faunes post-cretacees, 

 et que je distingue par les noms de Mosasatcridcs, Megalosauridce, et Iguanodon- 

 tidce.'' 1 — Extrait dcs Comptes Rendus des seances de V Academie des Sciences, 

 torn, xxxvi, seances des 28 fevrier et 14 mars, 1853, p. 5. 



