TAB. XXIII. 
Fig. 
1. Mactra ovalis, p. 246. 
a, 6, specimen from Mam. Crag, Chillesford. 
ce, d, specimen from Red Crag, Sutton. 
2. Mactra glauca, p. 241. From Red Crag, Newbourne. 
3. Mactra stultorum, p. 242. x Sutton. 
4. Mactra artopta, p. 244. - Sudbourne. 
5. Mactra arcuata, p. 243. 
a, specimen from Ramsholt, Cor. Crag. 
4, c, specimen from Walton Naze, Red Crag. 
