688 



PROF. OWEN ON THE RANK AND AFFINITIES IN 



by Cuvier (p. 319), are " sans explication osteologique " — that is, 

 have no symbols of reference to the constituent bones. 



§ 3. Upper Surface of the Cranium. — An ordinal characteristic 

 of Reptilia is afforded by the upper surface of the cranial and 

 cranio-zygomatic part of the skull. 



Fig. 5. 



Fig. 6. 



Mosasaurus. 

 Occipital region and upper surface of cranium. 



Cuvier gives a view of this surface in two genera of Crocodilia f ; 

 but of the Lacertilia he limits his figures to oblique side views ; and 

 corresponding views of the Ophidia are omitted. I therefore ap- 

 pend an upper view of the cranial characters in question in a Mosa- 

 sauroid, fig. 6, a Lacertian, fig. 7, and an Ophidian, fig. 8, in illus- 

 tration of the following remarks on this part of the skull. 



It is hardly necessary to do more than allude to the articulation 

 of the postfrontal with the mastoid in Crocodilia, and the strong 

 arch which these broad horizontally flattened bones send over the 

 temporal fossa, to which, in some species, they form a complete roof. 

 The parietal, also, is imperforate. If Cuvier had possessed the cor- 

 responding parts of the skull of a Mosasaur, he would doubtless 

 have added convincing grounds against Faujas's view of the croco- 

 dilian affinities of that genus, and in support of his own lacertian 

 conclusion. 



In the type Lacertilia (Monitor, Iguana, Amblyrhynchus, &c.) 

 the temporal fossae, t, are widely open. Each is bounded mesially by 

 the parietal, fig. 7, 7, laterally by the postfrontal, 12, and squa- 

 mosal, 27, posteriorly by the mastoid, 8. The parietal bifurcates 

 posteriorly, and develops a ridge from the hind part of the oblite- 

 rated sagittal suture, which ridge bifurcates anteriorly, arching for- 

 wards and outwards to the postfrontal, 12 ; the flat fore part of the 

 parietal, 7*, anterior to the latter bifurcation, is perforated by the 

 " foramen parietale," — in the Monitors and some other Lacertians, 



t Tom. cit. pi. iii. figs. 1 and 6. 



