270 



CAPT. i>. M. S. WATSON ON SEYMOURIA, 



in which unfortunately a, piece about 2*5 mm. thick is missing 

 from the middle of its height, this not having been collected. 



The exoccipital rests on the upper and lateral surface of the 

 basioccipital, meeting its fellow above that bone so as to form 

 the floor of the brain-cavity in the occipital regiou. Posteriorly 

 it projects behind the basioccipital and is provided with an arti- 

 cular face looking downwards and backwards which forms about 

 a quadrant of the occipital condyle. Above the body the bone is 

 continued up so as to form the side wall of the brain-cavity until 

 its posterior surface is overlapped by the occipital flange of the 

 dermo-supraoccipital. 



On the inner surface the exoccipital is excavated into a deep 

 pit from which a rather large hypoglossal foramen starts to pass 

 through the bone and open into the large vagus foramen. In 



Text-figure 2. 



Seymouria bayloriensis Broili. — Restoration of tlie occipital view, X f. 



Membrane-bones from Munich A. Quadrate from a young individual collected 

 by the writer. Occiput from my skeleton. 



Reference letters as before with : — D.S.Oc., dermo-supraoccipital ; Fen.Ov., fenestra 

 ovalis; Qu.J., quadrato-jugal ; Sq., squamosal ; Tab., tabular. 



front of the ridge which • bounds the hypoglossal foramen 

 anteriorly, the inner surface of the exoccipital turns outward 

 and forms the posterior margin of the foramen for the Xth 

 nerve. The upper end of the exoccipital is fused with the par- 

 occipital, no suture being visible. It approaches its fellow of the 

 opposite side over the foramen magnum, but leaves a space for 

 the cartilaginous supraoccipital. In my skull the space where 

 the supraoccipital should be is entirely free from bone, but in the 

 type of Conodectes there is some evidence of a slight supra- 

 occipital ossification. 



Paroccipital. — The paroccipital is fused with the exoccipital on 

 the back of the skull. It is separated from the lower part of 

 that bone by a large notch, the foramen for the vagus nerve. 



