PLATE LXV. 



Zone of Lytoceras Jurense. 



Fig. 1. Harpoceras insigne, Schubler. Side view, natural size. My collection. 



2. — — — Front view, showing ribs and keel, natural 



size. 



3. — — — Back view, do. do. 



4. — — — Variety with spinous sides, do. 



5. — — — Do,, front view, do. 



6. — — — Lobe-line, magnified, do. 



