310 Annals of the South African Museum. 



limb bones, including portions of the femora, tibiae, fibulae, and a 

 number of phalanges. These show that the animal was a typical 

 Plesiosaur, and, in the absence of the pectoral girdle, I see no 

 sufficient reason to regard it as other than a species of the genus 

 Plesiosaurus. It will be shown below that it differs in several 

 respects from other known species from approximately contem- 

 porary deposits, and it is therefore regarded as a new species, for 

 which the name Plesiosaurus capcnsis is suggested. 



The skull (PI. XVIII., Fig. 1, text-Fig. 1) is in a fair state of preserva- 

 tion : nearly the whole of the palatal surface can be seen, but of the 

 dorsal surface the greater part of the left side is concealed by the 

 neural spines of six dorsal vertebrae which have been crushed down 

 upon it. Part of the sub-orbital region of the right side and the 

 right zygomatic arch are missing, and the zygoma of the left side is 

 in part concealed by matrix. Between the temporal fossae the 

 parietals probably formed a well-marked sharp crest, but for the 

 most part this has been broken away. The snout is narrow, and at 

 the point where the maxillo-premaxillary suture crosses the alveolar 

 border there is a slight constriction. The greatest width of the 

 skull is between the outer ends of the quadrates, and this measure- 

 ment is to the length of the skull from the occipital condyle to the 

 tip of the snout, about as 2 to 3. 



The basi-occipital (b.oc.) appears to bear the whole of the occipital 

 condyle, which is sessile and considerably wider than high. Beneath 

 the condyle there is a narrow vertical surface, running out laterally 

 on to the posterior face of the postero-lateral (pterygoid) processes. 

 The lower ends of these, and indeed the whole ventral face of the 

 basi-occipital, are covered by the pterygoids, which meet in the 

 middle line. It is not possible to make out the sutures between the 

 basi-occipital and the exoccipital-opisthotics. The latter are, so far 

 as can be seen, similar to the same elements in the other Plesio- 

 saurs ; that is to say, they consist of a columnar portion forming the 

 sides of the foramen magnum and uniting above with the supra- 

 occipital, and a long paroccipital process which runs outwards, 

 downwards and backwards to the quadrate (q.), with which its outer 

 end was probably in contact, though possibly it joined the outer end 

 of the quadrate process of the pterygoid, the sutures in this region 

 being very indistinct. 



The supra-occipital forming the upper part of the foramen 

 magnum is crushed over to the left, and the shape of the opening 

 thereby distorted. At its upper end the supra-occipital united with 

 parietals, but its precise relations with those bones cannot be made 



