PLATE XXII a. 



Zone of Amaltheus oxynotus. 



Fig. 1. Arietites impendens, Young 8r Bird. Side view, natural size. Woodwardian 



Museum, Cambridge. 



2. — — — Front view of the same shell. 



3. — — — Siphonal area of do. do. 



4. — — — Young shell with sharp ribs and 



sulci. 



5. — — — The lobe-line magnified. 



6. — Collenottii, d' Orbiqny. Side view, natural size. Woodwardian 



Museum, Cambridge. 



7. — — ■ Front view of same shell. 



8. — — — Siphonal area of do. do. 



9. — The lobe-line, highly magnified. 



