8 



BRITISH FOSSILS. 



Ireland Colonel Portlock observed Forma a ovata to be cbarac- 

 teristic of the lower beds there. In England that variety is chiefly 

 from the upper beds. All the varieties occur as flint casts among 

 gravel. 



Specimens with slightly tumid plates from County Derrylin 

 Ireland were referred by Portlock to the Ananchytes sulcatus of 

 Goldfass, a Maestricht species. They are, however, unquestionably 

 only peculiar examples of A. ovatus. The supposed British Hemi- 

 'pneustes radiatus recorded by Dr. Mantell is only Ananchytes 

 ovatus, as the original examples in the British Museum show. 



ExPLAJfATION OF PlATE IV. 



Pigs. 1. 2. and 3. Different views of an example of the common Forma a. 



Fig. 4. Forma e pyramidatus from the original specimen. 



Fig. 5. A very unsymmetrical example of Forma t. 



Fig. 6. A similar example more tumid in outline. 



Fig. 7. A subglobular specimen, Forma 5. 



Fig. 8. A much elongated example of Forma /3, 



Fig. 9. A very elevated example of Forma 7. 



Fig. 10. The plates of the apical disk. 



Fig. 11. The interior impressions of the apical disk as seen upon a flint cast, showing the 



furrow indicating the position of the base of the sand canal. 

 Fig. 12. Ambulacral and interambulacral plates from near the apex. 

 Fig. 13. Similar plates from the sides. 

 Fig. 14. Tubercles and granules of the upper surface. 

 Fig. 15. Tubercles and granules of the lower surface. 



October, 1852. Edward Forbes. 



