PLATE LIIa. 



Zone of Aegoceras Jamesoni. 



Fig. 1. Aegoceras sagittarium, Blale. Side view, variety a, natural size. My collec- 

 tion. 



2. — — — Siphonal area, do. do. 



3. — — — Side view, natural size. do. 



4. — — — Front view, do. 



5. — — — Side view, do. do. 



6. — — — Siphonal area, do. 



