PLATE LXXVII. 



Fig. 1. Phylloceras Zetes, d' Orbigny. Side view, natural size. My collection. 



2. — — — Front view, siphonal area and aperture. 



3. — — — Suture-line, magnified. 



4. — heterophyllum, Sowerby. Suture-line magnified to compare 



with that of Phylloceras Zetes. 



