PLATE XVII. 



Zone of Ae(/oceras angulatum. 



Fig. I. Aegoceras angulatum, Schlotheim = PiMmonv^^^ M.OR^A.NVS,d'Ordign^. Side 



view, natural size. Lyme Regis. My 

 collection. 



2. — — — Front view of the siphonal area of the 



same fossil showing the rib termina- 

 tions. 



3. — — — Lateral view of ribbing in another specimen 



from the same bed. 



4. — — — Continuous ribbing over the siphonal area 



in the same specimen. 



5. — — — Smaller and closer ribbed variety from 



the same bed, natural size. 



6. — — — Siphonal area with interrupted ribbing, 



forming angles in the same. 



