PLATE XII. 
Page. 
Fig. 1. W. Martin — Adult specimen, seen from the dorsal side ... 177 
Fig. la. The same, seen in profile ... ... ... ... ... ... ... ... 177 
Fig. Ih. Internal cast, seen from the ventral side ... ... ... ... ... ... 177 
Fig. Ic. Another internal cast, seen from the dorsal side , ... ... ... ... 177 
Fig. 2. Spirifer convolutus, J. Phillips — Large specimen, drawn from a mould in plaster, 
seen from the dorsal side ... ... ... ... ... ... ... 187 
Fig. 3. Spirifer oviformis, F. McCoy — Internal cast, seen from the dorsal side... ... 181 
Fig. 3fl. The same, seen from the ventral side ... ... ... ... ... ... 181 
Fig. 35. ,, seen in profile ... ... ... ... ... ... ... 181 
Fig. 3c. ,, seen from the front ... ... ... ... ... ... ... 181 
Fig. 4. Spirifer diwJecimcostatns, F. McCoy — Ventral valve, seen from the front ... 182 
Fig. 4ff. Internal cast of the ventral valve ... ... ... ... ... ... ••• 182 
