PLATE LX. 



Zone of Harpoceras bifrons. 



Fig. 1. Harpoceras Levisoni, /Sew^so;?. Side view, natural size, showing side aperture, 



lobes, process, and lobe-line. My collec- 

 tion. 

 2, — — — Siphonal area and keel, natural size. 



