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The specimen in question no. E. 1021, Brit. Mus., Nat. Hist., 

 figured by Seeley, Phil. Trans., B, 1889, PI. 10, figs. 1 & 2, consists 

 solely of the occipital and otic bones with part of the basisphenoid. 



The Basioccipital has a large condyle which forms the lower 

 part of the ordinary tripartite condyle: its upper surface supports 

 the exoccipitals, which meet in the middle line so as to exclude the 

 basioccipital from the foramen magnum, the suture separating these 

 bones forks in front each branch running out to a notch formed 

 by the basioccipital, basisphenoid and exoccipital which forms the 

 inner border of the confluent foramen jugularis and internal auditory 

 meatus: between these notches the bone is very narrow and it is 

 no doubt in this region that the suture with the basisphenoid is to 

 be found. The lower surface of the basioccipital decends steeply 

 to the front from the under surface of the condylar pedicle and its 

 lateral borders are deflected as thin flanges covering the inner side 

 of the processes of the opisthotics which carry the fenestra ovale down 

 below the base of the skull. 



The anterior end of the basioccipital is articulated with the 

 basisphenoid, the suture separating the bones being often visible 

 on the ventral surface. The postero-lateral borders of the basisphenoid 

 are carried down as thin flanges on the inner side of the decending 

 processes of the pro-otics which join with the corresponding processes 

 of the opisthotic to form the fenestra ovale: in front of this region 

 the bone is pierced by a pair of foramina, or in Endothiodon a single 

 foramen, for the internal carotid: still further forward the bone 

 narrows to a point whose lower and lateral faces are roughened by 

 the attachment surfaces for the vomer and the pterygoids, there 

 being no distinct basipterygoid processes. The lateral surfaces of the 

 body of the basisphenoid are completely covered by the prootics. 

 The upper surface, which forms part of the floor of the brain cavity, 

 contributes to the internal auditory meatus, is separated by suture 

 from the prootic and in front of this bone drops very steeply to form 

 the pituitory fossa, into which the carotid canals open. 



The exoccipitals are fused with the opisthotics, they form the 

 upper part of the tripartite condyle, meeting in the middle line, only 

 a small part of the lateral border of the foramen magnum is formed 

 by them; viewed from within each forms the back of the foramen 

 jugularis between which and the posterior border it is pierced by a 

 foramen for the Xllth, nerve which opens into a canal which joins 



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