PLATE XXVIII. 



PlSIDIUM STEENBUCHII (Mdllel). 



2. External right aspect of a pair from Abbey Holme, 



Cumberland. 



3. of a pair from Bjerking, Malselvdalen, Norway. 



("P.globulare, Clessin.") 



4. Internal aspect of a left valve from Abbey Holme, 



Cumberland. 



5. External right aspect of a pair from Grisel Bottom, 



Burwell Wood, Lincolnshire. 



6. of a pair from West Greenland. 



7. , b. Posterior and dorsal view of a pair from the same locality. 



8. a, b. of a pair from Grisel Bottom, Burwell Wood, 



Lincolnshire. 



10. a, b. Internal aspect of a pair from West Greenland. 



11. a, b. of a pair from Grisel Bottom, Bur well Wood, 



Lincolnshire. 



14. Diagrammatic enlargement of the Hinge. 



15. , 6. Internal aspect of a pair from Bjerking, Malselvdalen, 



Norway* (" P. ylobuhire, Clessin.") 



16. a, b. of a pair from Finmarken, Norway. ("/ J . globu- 



lar e, Clessin.") 



PlSIDIUM LILLJEBORGII, CleSSin. 



1. a-c. External right aspect of three pairs from Lochan a' Chait, 



Perthshire. 

 9* a, b. Posterior and dorsal view of a pair from the same 



locality. 



no* a> i' r Internal aspect of two pairs from the same locality. 

 lo. , 6 J 



17. a-c. External right aspect of three pairs from Sonset, Norway. 



(Clessin.) 



18. a, b. Posterior and dorsal view of a pair from Lough Aguse, 



Co. Fermanagh. 



19. a f &. of a pair from Sonset, Norway. (Clessin.) 



20. a-d. External aspect of four valves from the Holocene at 



Gayfield, Edinburgh. 



21. a-d. of four valves from the Pleistocene at Crayford- 



Erith, Kent. 



22. a-j. Internal aspect of five pairs showing variation, from 



Sonset, Norway. (Clessin.) 



23. Diagrammatic enlargement of the Hinge. 



24. a-d. Internal aspect of four Valves from the Holocene at 



Gayfield, Edinburgh. 



25. a -f. of three pairs from Lough Aguse, Co. Fermanagh. 



26. a-f. of six valves from the Pleistocene at Crayford- 



Erith, Kent. 



*** The scale in millimetres under each figure) or series of figures, 

 shows the amount of magnification. 



