BY PROFESSOR STEPHENS, M.A., F.G.S. 1183 



observers. The centrum seems to have been only cartilaginous. At 

 least I can see no trace of it. [In Gondwanosaurus, each vertebra 

 consisted originally of a bony neural arch, from which a bony 

 plate descended on each side, and joined a median ventral portion. 

 The intervening inferior portions of the column being represented 

 by unossified remains of the notochord.] The Vertebra? number 

 sixteen (16) from the posterior termination of the medial plate, to 

 the indication of a pelvis. There is no appearance of a sacrum. 

 It appears as if the number of vertebras in advance of the posterior 

 end of the throat plate was eight (8), and these, together with 

 their appendages, seem to have been in the process of fossilisation 

 crushed down into, and amalgamated with, the thoracic plates which 

 lie beneath them. For it can hardly be questioned, as shown 

 above, that we have the inner or upper surface of these plates 

 exposed, that is, that the spinal column lies between them and 

 our eyes, and that consequently any portions of the spine which 

 may, from whatever cause, appear to be beneath this inner or upper 

 face are nevertheless in reality above it, although perhaps sunk 

 into or through the surface, Some such portions of these anterior 

 vertebras, similar in every respect to those behind them, are quite 

 distinctly visible, and appear, the ribs especially, as if they lay in 

 an impossible situation beneath them. I can only suggest, as a 

 possible explanation of this contradiction, that the process of 

 mineralization, by which calcite has been deposited in the radiations 

 of the plates, has also effected a similar deposition in the slight and 

 scarcely solid bones which were pressed down upon them. 



[On second thoughts I am led to the conclusion that the ribs 

 and vertebras, which seem to stand out in low relief upon the 

 surface of the plates, and nevertheless to be crossed by the white 

 lines of calcite as if they were seen through their substance, are in 

 reality impressions in relief from Moulds in intaglio formed by 

 the shrinking or flattening of very imperfectly ossified bones or 

 cartilages ; and that thus these reliefs are casts, or squeezes, in 

 the soft and thin but horny material of the plates, these being 

 pressed upwards into the aforesaid Moulds.] 

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