988 DR F. R. C. REED ON THE 



Plate XV. 



Fig. 1. Plectambonites seiHcea (Sow.), var. nov. albida. Brachial valve. x 4. Whitehouse Group, 

 Wliitehouse Bay. G. 



Fig. 2. Ditto, ditto. x 4. Same horizon and locality. G. 



Fig. 3. Ditto, ditto. x 3. Same horizon and locality. G. 



Fig. 4. Plectambonites sericea (Sow.), var. nov. conspicua. Interior of brachial valve, x 1^. Stiuchar 

 Limestone Group, Craighead. G. 



Fig. 5. Ditto. Posterior view of interior of brachial valve. x 1^. Same horizon and locality. (!. 



Fig. 6. Ditto. Outline side-view of ditto. Nat. size. Same horizon and locality. G. 



Fig. 7. Ditto. Pedicle-valve. x 1£. Same horizon and locality. G. 



Fig. 8. Ditto. Right side of pedicle-valve. x 1£. Same horizon and locality. G. 



Fig. 8a. Ditto. Portion of surface of same specimen. x 6. 



Fig. 8b. Ditto. Median longitudinal section of same complete shell. x \\. 



Fig. 9. Ditto. Outline of complete shell. Nat. size. Balclatchie Group (conglom.), Balclatchic. G. 



Fig. 10. Ditto. Median longitudinal section of same shell. Nat. size. 



Fig. 11. Ditto. Diagrammatic transverse section showing carination of pedicle-valve. 



Fig. 12. Plectambonites sericea (Sow.), var. nov. craigensis. Pedicle-valve. x 3. Stinchar Limestone 

 Group, Craighead. G. 



Fig. 13. Ditto. Internal cast of brachial valve. x 4. Same horizon and locality. G. 



Fig. 14. Ditto. Internal cast of pedicle-valve. x 4. Same horizon and locality. G. 



Fig. 15. Ditto. Pedicle-valve. x 3. Same horizon and locality. G. 



Fig. 16. Ditto, ditto. x 4. Same horizon and locality. G. 



Fig. 17. Ditto. Internal cast of pedicle- valve. x 4. Same horizon and locality. G. 



Fig. 18. Plectambonites sericea (Sow.), var. nov. semirugata. External impression of pedicle- valve, 

 x 3. Balclatchie Group, Ardmillan. G. 



Fig. 19. Ditto. External impression of brachial Valve of same shell. x 3. Same horizon and 

 locality. G. 



Fig. 20. Ditto. External impression of pedicle-valve. x 3. Same horizon and locality. G. 



Fig. 21. Ditto. Internal cast of same shell, x 3. Same horizon and locality. G. 



Fig. 22. Ditto. Internal cast of brachial valve. x 3. Same horizon and locality. G. 



Fig. 23. Ditto, ditto. x 3. Same horizon and locality. G. 



Fig. 24. Ditto. External impression of brachial valve. x 3. Same horizon and locality. G. 



Fig. 25. Ditto. Internal cast of brachial valve. x 3. Same horizon and locality. G. 



Fig. 26. Ditto. Internal cast of pedicle-valve. x 2|. Same horizon, Balclatchie. G. 



Fig. 27. Plectambonites sericea (Sow.), var. nov. thraivensis. Pedicle-valve. x 4. Drummuck Group, 

 Thraive Glen. G. 



Fig. 28. Ditto, ditto. x 3. Same horizon and locality. G. 



Fig. 29. Ditto, ditto. x 3. Same horizon and locality. G. 



Fig. 30. Ditto. Internal cast of pedicle-valve. x 3. Same horizon (Starfish Bed) and locality. G. 



Fig. 31. Ditto. Internal cast of brachial valve, x 4. Same horizon (Starfish Bed) and locality. G. 



Fig. 32. Ditto. External impression of brachial valve showing cardinal areas of both valves, x 1\. 

 Same horizon (Starfish Bed) and locality. G. 



Fig. 33. Plectambonites subcorrugatella, sp. nov. Pedicle-valve. x 2. Wliitehouse Group, Shalloch 

 Mill. G. 



Fig. 34. Ditto. Brachial valve, exterior. x 2 J. Same horizon and locality. G. 



Fig. 34a. Ditto, ditto. Interior of same specimen, x 2£. 



Fig. 35. Plectambonites transversalis (Dalm.). Pedicle-valve. x 1|. Saugh Hill Group, Woodland 

 Point. G. 



Fig. 36. Ditto, ditto. x 2. Same horizon and locality. G. 



Fig. 37. Plectambonites transversalis (Dalm.), var. Duvali, Dav. Pedicle-valve. x 2£. Same horizon 

 and locality. G. 



Fig. 38. Ditto, ditto. x 2. Same horizon and locality. G. 



