PLATE LIX. 



Zone of Harpoceras bifrons. 



Fig. 1. Harpoceras bifrons, Brucjuiere, Side view, lobe-line aperture and laten 



processes, natural size. My coliection. 



2. — — — Siphonal area with lobe-line do. do. 



3. — — — Fragment of a small shell with groove. 



4. — — — Do. do. do. 



