PLATE LXXX. 



Zone of Harpoceras opalinum. 



Fig. 1. Harpoceras Aalense, Zieten. Side view, natural size, with shell. Adult form, 



Coaley Wood. My collection. 



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



3. — — — Suture line of do. magnified. 



4. — opalinum, Beinecke. Side view, natural size. Frocester Hill. 



My collection. 



5. — — — Suture line of do. magnified. 



6. — — — Large specimen, natural size. My collec- 



tion from Haresfield. 



7. — — — Front view of the same, natural size. 



8. — — — View of siphonal area. 



