Xll 



MARINE REPTILES OF THE OXFORD CLAY. 



and there is a space large enough for one centrum, probahly the last cervical. The 

 next vertebra has the parapophysis almost entirely on the arch and is here regarded as 

 the first dorsal — if rightly so, there are nineteen dorsals altogether. In all, the 

 transverse processes are broken away, but the neural spines, which are broad, low, and 

 sloping a little backwards, are well preserved. The two sacrals are much obscured by 

 the crushing that has taken place, the right ilium having apparently been forced down 

 upon them and destroyed ; the neural spines are similar to those of the dorsal 

 region. 



The caudal vertebrae (text-fig. A) are about fifty in number, and of these 

 twenty-seven are in front of the downward flexure of the tail. E. Fraas states that in 



Text-fig. A. 



Ik 



Terminal portion of tail of Geosaurus gracilis, showing the outline of the fin. (R. 3948, | nat. size.) 



Geosaurus suevicus there are forty-four caudals, but possibly some of the very small 

 terminal centra, here preserved, may be wanting in his specimen. Caudal ribs seem 

 to have been present on the first fourteen vertebrae, but on the last two of these they 

 merely form slight prominences. The neural spines are not well preserved in the first 

 few caudals, but further back it can be seen that they are composed of a larger back- 

 wardly sloping portion separated by a notch from a small anterior pointed process (the 

 " Vorreiter " of Fraas). From the sixteenth to the twenty-fifth the neural spines are 

 not well preserved, but on the twenty-sixth and twenty-seventh (the two immediately 

 anterior to the downward bend) they are seen to slope sharply backwards and are 



