PLATE LXXIV. 



Zone of Lytoceras Jurense. 



Fig. 1. Harpoceras radians, Reinecke. Side view, natural size. My collection. 



2. — — — Front view, showing carina, siphonal area, and 



aperture. 



3. Lytoceras Jurense, Zieten. Side view, natural size. My collection. 



4. — — — Front view of same. 



5. — — — Abdominal view of same. 



