PLATE XXXIX. 



Genus — Plectomya, de Lnriol. 

 Figs. 

 1. P. angliai, Woods. Lower Greensand (Crackers), Atlierfield. Sedgwick 

 Museum, Cambridge. a, right valve; Ji, ornamentation X 16. 

 (P. 238.) 



Genus — Anatina , La ma rrl: 

 2 — 4. /]. (Cercomija) gurgifis, Pict. and Camp. Lower Greensand. (P. 230.) 



2. Perna-hei, Isle of Wight. British Museum, No. L436. Eight valve. 



3. Crackersj Atlierfield. Sedgwick Museum, a, part of left valve ; b, dorsal 



view ; c, oruameutatiou near the autero-veutral margin x 12. 



4. Crackers, Atlierfield. Sedgwick Museum, a, left valve ; 6, ornamentation 



near the autero-veutral margin x 10. 



5. A. {Gerconiija) sp. Upper Greensand, Isle of Wiglit. British Museum, 



No. 48626. Internal cast. «, right valve; /^ dorsal view. (P. 239.) 



6. A. (Ccrromi/a) sp. Upper Greensand, Warminster. Briti.sli Museum, 



No. 88926. Internal cast of part of right valve. (P. 240.) 



Genxs — Thraoia, Leach. 



7_(). T. riiiUljisi, Rum. Speeton Clay, Speeton. (P. 21().) 



7. Mr. Slather's CoUectiou. a, right valve ; b, dorsal view. 



8. Sedgwick Museum. Eight valve. 



9. Sedgwick Museum. Left valve. 



10. T.rotundata (How.). Hythe Beds, Lympne. Museum of Practical Geology, 

 No. 23470. a, right valve; h, dorsal view. [V. 241.) 



