REPTILIA. 



(fig. 315) is pyramidal, and the jaws do not exhibit any traces 

 of teeth. If the mouth be really edentulous, then Rhynchosau- 

 rus should probably be removed from the Lacertilia\ but this 

 point cannot in the meanwhile be definitely decided in the 

 affirmative. 



Amongst other Triassic, or supposed Triassic, Lacertilians, 

 may be mentioned Saurosternon and Pristerodon^ from strata 

 believed to be of Triassic age in Africa, and Clepsysanrus and 

 Centemodon from deposits of the same age in North America. 



In the Jurassic period, the remains of Lacertilians are not 

 unknown, but call for little special notice. Several forms of 

 little importance have been described from the Middle Oolites. 

 In the fresh-water strata of the Purbeck series (Upper Oolites), 

 occur the remains which have been referred to the genera 

 Nuthetes, Macellodon, Saurillus, and Echinodon. These are, 

 perhaps, the first traces in the stratified series of remains, the 

 affinities of which to the typical Lacertidce. cannot be disputed. 



In the Cretaceous series occur the small Lizards which con- 

 stitute the genera Raphiosaurus, Coniosaums, and Dolichosau- 

 rus. Here also, and almost exclusively confined to strata of 

 this age, occur the singular Lacertilians which form the group 

 of the " Mosasauroids." These remarkable Reptiles were of 

 gigantic size, Mosasaurus princeps being believed to have at- 

 tained the enormous length of not less than seventy-five feet. 

 The teeth in these reptiles (fig. 316) are long, pyramidal, and 



Fig. 316. Skull of Mosasaurus Cam/eri, much reduced. Maastricht Chalk. 



slightly curved ; but they are anchylosed to the jaw, and are 

 not sunk into distinct sockets, as in the living Crocodiles. 



