PLATE X. 



Fig. 



1 — 3. Ammonitf.s prramplus. 



\a and d. An old specinnen, figure reduced to one half its diameter; from the 

 Middle Chalk of Wiltshire, in the collection of Mr. Cunnington. 



2. Specimen of intermediate age, of the natural size; from the 

 Middle Chalk of Hemel Hampstead, in the collection of the 

 Geological Society : with the outline of one of its septa. 



3^/ and d. Young specimen of the natural size ; from the Middle Chalk of 

 Wiltshire, in the collection of Mr. Cunnington. 



