PLATE XXI. 



PAGE 



Fig 10. AMMONITES BATESII. Showing the gradation from the angulated 

 whorls of the young state of this variety, to the rounded whorls 

 in the older shell. 132 



10 a. Cross section of shell. 

 10 b. Septum 



Fig. 11. A. StHHAEN&IS 133 



11 a. Cross section of body whorl. 

 11 b. Septum. 





