METEI0EHYNCHTJ3. 



1C7 



facets. In the anterior part of the tail the neural arches are borne on pedicles which 

 extend nearly the whole length of the centrum. The anterior zygapophyses are small 

 and closely embrace the posterior zygapophyses of the preceding vertebra ; these are 

 situated at the lower end of the posterior edge of the neural spine. The neural spine 

 (n.sj).) varies much in form in different parts of the column. Unfortunately, none of 

 the anterior caudals examined have the neural spines well preserved, so that it is not 

 possible to see whether the notching of their anterior edge, described by Fraas * in the 

 case of Geosaurus, begins in the same way ; but further back in the column the 

 spines are quite similar to those found in that genus, consisting of a small anterior 

 pointed process (a.]).), projecting upwards above the anterior zygapophysis (a.z.), and a 

 large backwardly sloping portion (n.sp.), which constitutes the main body of the spine. 



Text-fig. 66. 



Vertebras at bend of tail of JHetriorhynehus cultrulens, from left side. (B. 3804, | nat. size.) 



a.z., anterior zygapophysis ; c, chevron ; c.f., chevron-facets ; n.sp., neural spine : 

 p.z., posterior zygapophysis. 



This latter in the anterior part of the tail is strongly compressed from side to side and 

 terminates above in a rounded border ; as before noted, the posterior zygapophyses are 

 situated on either side of the lower end of the main part of the spine. As this type of 

 neural spine is followed backwards in the series it becomes gradually smaller and slopes 

 backwards to a greater degree. On the vertebra? immediately in front of the bend 

 (text-figs. Go D, 66) the neural spine is still directed backwards, but becomes much 

 thickened, and the posterior zygapophyses are greatly reduced or absent. In the next 



* Palceontograpbica, vol. xlix. (1802) p. 52. 



