286 FOSSIL REPTILES. 



This last is narrow, and a little crooked towards the summit. 

 It is chiefly formed by a temporal of similar configuration, 

 which is closely united by its posterior extremity to the mas- 

 toid. The mastoid is equally narrow and crooked, and is simi- 

 larly fastened on the lateral point of the parietal. 



The parietal is in the form of a buckler, widened in front, 

 hollowed on the sides of the two temporal fossae, furcated be- 

 hind, and giving out there two long points, which, with the 

 temporal and jugal, and a salient apophysis of the lateral occi- 

 pital, proceed to give a point of suspension to the tympanic 

 bone. 



A foramen should be remarked which is naturally pierced 

 in the parietal bone, very nearly towards the centre, and which 

 is again found in many of the Saurian reptiles, and even in 

 the ichthyosaurus. 



In the bifurcation of the parietal behind is placed the upper 

 occipital, which attaches to the emargination of the parietal 

 only by a round ligament, and not by a suture. The ossa 

 petrosa are tolerably extended, and cover, both at top and in 

 front, the vacancy which remains on each side between the 

 occipitals and the sphenoid. 



Besides the vacant space which descends into the temporal 

 fossa, between the parietal, the posterior frontal, and the tem- 

 poral, there is another which penetrates behind, between the 

 point of the parietal, and the occipitals. These are great 

 spaces which correspond to the foramina which exist in the 

 crocodiles, but which are much smaller, because there the bones 

 are less dilated. 



Th& fenestra ovalis is, as usual, common to the os petrosum 

 and to the lateral occipital. 



The fenestra rotunda is pierced in a fossa of the lateral oc- 

 cipital. This last bone proceeds laterally, having the os 

 petrosum before it to unite by its external extremity to the 

 lower extremity of the mastoid, on the outside of which also 

 terminates that of the temporal. 



