PLATE III 



FIG. i. Trigonia clavellata with the ligament preserved. Corallian, 

 Weymouth. 



FIG. 2. Trigonia incurva. Internal mould. Portlandian, Swindon. 



FIG. 3. Angelina sedgwicki. Distorted^by cleavage. Tremadoc slates, 

 Minfford, N. Wales. 



FIG. 4. Glycimeris glycimeris. Pliocene, Suffolk. Thejaragonite shell is 

 crumbling. 



FIG. 5. Ostrea edulis. Pliocene, Suffolk. The calcite shell is in perfect 

 preservation. 



