PLATE V. 



Zone of Arietites BucMandi. 



Fig. 1. Arietites rotiformis, Sowerby. Lateral view, natural size, of the original 

 type specimen figured by the late Mr. James De C. Sowerby in the 

 'Mineral Conchology ' in 1825, from an example collected near Yeovil, 

 and now in the British Museum. This fossil has a very rugged surface, 

 owing to the shell having become decomposed in patches on the ribs and 

 other parts. 



2. View of the siphonal area of the same specimen, with the siphonal foliations in 



situ. Natural size. 



3. Front view of the same, showing tubercles, keel, and bisulcations. Natural size. 



4. View of the siphonal area of a large example from Lyme Regis, showing the 



shell-structure, keel, bisulcations, and siphonal ribs. Natural size. 



