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Annals of the South African Museum. 



and dorsals that are preserved. In the anterior cervicals (PI. XVIII., 

 Figs. 5, 6) the centra are considerably wider than long ; their 

 articular faces are wider than high and are deeply concave, the 

 centre being occupied by a large sharply defined fossa (Fig. 6). 

 This depression seems to be more deeply excavated on the posterior 

 than on the anterior face, and is particularly sharply defined in the 

 more anterior vertebras. In these also the centra bear a sharp hypa- 



(Z.Z 



2. Posterior cervical vertebrae of Plesiosaurus capensis ; from left side. About 

 nat. size. 



a.z., anterior zygapophysis ; c.r., bases of cervical ribs; n. sp., neural 

 spine; p.z., posterior zygapophysis. 



pophysial ridge (Fig. 5a), which is as it were pinched up and has 

 on either side of it a concave surface ; near its anterior end there are 

 in some cases small sharp lateral projections which probably served 

 for the insertion of tendons. On either side of the ridge and close 

 to it are the nutritive foramina. The cervical ribs are fused with 

 the ventro-lateral borders of the centra, and above them the sides of 

 the centra are concave both from side to side and from above down- 

 wards. The neural arch is high and is fused with the centrum ; the 



