PLATE LXVII. 



Zone of Lytoceras Jurense. 



Fig. 1. Harpoceras variabile, (T Orbigvy. Side view, natural size. My collection, 

 2. — — — Front view, showing siphuncle, do. 



3 — 6, — — — Different forms of varieties of the species, 



do. iMy collection. 



