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VIII. — Report on the Reptilian Fossils of South Africa. 



Part III. — On parts of the Skeleton of the Trunk of the Dicynodon tigriceps. 

 By Professor OWEN, F.R.S., F.G.S. 



[Read June 13th, 1855.] 



Plates XXXIII. and XXXIV. 



JMaNY of the nodules of the hard rock which forms the matrix of the skull of the 

 Dicynodon tigriceps contained bones which belonged to other parts of the skeleton : 

 some of these have been more or less relieved from their bed, and the following are 

 amongst the best-preserved and most intelligible specimens at present exposed. 



Vertebrce. — In the first part of the present Report on the Reptilian Fossils of 

 South Africa, I briefly noticed the biconcave structure of the vertebrae of the 

 Dicynodon, as indicating " a more aquatic and perhaps marine tkeatre of life" for 

 these ancient African Saurians, than any existing species of that order are now 

 known to manifest in that continent. {Vide supra, p. 83.) 



A vertebra (Pl. XXXIII. figs, 1-3), from the anterior part of the dorsal region, 

 seems to belong, from the proportion which its articular surface bears to the con- 

 dyle of the occiput of the Dicynodon tigriceps, to the same species, or at all events, to 

 an individual of the same size. As it was imbedded in the same block with a skull 

 and other bones of the Dicynodon tigriceps, it is most probably of the same species. 



The centrum and neural arch are partially anchylosed, with definite traces of the 

 suture, which is in the usual position {n). The centrum is short ; the contour of 

 the articular surface is subcircular ; the margin is convex for about three lines, 

 and then the surface sinks into a deep conical concavity, the apex of which nearly 

 meets that of the concavity of the opposite articular surface (fig. 3). The non- 

 articular surface is smooth, moderately concave lengthwise, impressed at the 

 upper and anterior angle of the centrum with the lower half of a vertically oval 

 concave surface (p), for the articulation of the head of a rib. 



The base of the neurapophysis (w) is coextensive with the centrum ; as it rises, it 

 is slightly emarginate before and behind for the outlet of the nerves, and is 

 extended outwards in the form of an oblique ridge. The neural canal is sub- 

 circular ; above its anterior outlet are the bases of a pair of zygapophyses (z). 

 The strong oblique ridge which rises from the outer and fore part of the base of 

 the neurapophysis extends backwards, as it rises, to support the diapophysis {d) ; 

 the base of this process is of great strength, and extends outwards and rather 



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