PLATE LXXXVI. 



Zone of Stephanoceras commune. 



Fig. 1. Stephanoceras crassum, Young. Side view, natural size. Whitby. My col- 

 lection. 



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



3. — Braunianum, aVOrbigny. View of siphonal area magnified two 



and a half diameters. My collection. 



4. — — — Side view of same shell, showing 



tubercles and costation magnified 

 two and a half diameters. 



5. — Raquinianum, — Siphonal area magnified two dia- 



meters, with suture line in situ. 

 Nailsworth. Upper Lias Sands. 

 My collection. 



6. — — — Side view of the same fossil, showing 



the position of the tubercles and 

 lateral costae ; two diameters. 



7. — — — Front view of the same, showing 



regular transverse costae. 



8. — crassum, Young. Large, well-developed specimen showing 



siphonal area, thick transverse costae, and 

 lateral tubercles in situ. Whitby. My 

 collection. 



9. — — — Lateral view of the same fossil, showing 



the strong costae and thick whorls. 

 10. — — — Front view of the same shell, showing 



transverse costae and oral aperture. 



