PLATE XXVIII. 
Zone of Aegoceras armatum. 
Fig, I. Aegoceras armatum, Sowerhy. Side view, natural size. A very fine type 
specimen. Leckenby collection. Wood- 
wardian Museum, Cambridge. 
2. — — — Front view, showing the ribs and spines in 
profile. 
3. — ■ ■ — — Smaller specimen in same collection. 
4. — — — Siphonal area, showing spines of the left side' 
absent. 
5. — — — Another specimen, showing spines of the left 
side truncated. My collection. 
6. — — — A very accurate tracing from another specimen 
of the highly complicated lobe-line, showing 
the large size of the siphonal and principal 
lateral lobes. My collection. 
