PLATE IV. 



Fig. Page. 



1. Oxy discus acut US (Sow.). Internal cast. Side view of type, x 2. Bala 



Series, Horderley. Mas. Pract. Geol. [6916]. 19. 



la. Dorsal view. X 2. lb. Front view. X 2. 



2. Ditto. Side view of specimen with shell preserved showing ornament. 



X 2. Bala Series, Onny River. Mus. Pract. Geol. [28024]. 19. 



2a. Restored dorsal view. X 2. 



3. OceijtlisrAis hougangensis, 8]). noY. Side view. X 1^. Stinchar Limestone, 



Bougang. Mrs. Gray's Coll. 20. 



3a. Restored dorsal view. X I4. 



4. Oxydiscus hunteri, sp. nov. Side view of specimen with shell preserved. 



X H- Balclatchie Group, Balclatchie. Mrs. Gray's Coll. 20. 



4<n. Dorsal view. X 1^. 4/>. Ornament. X 10. 



5. Ditto. Internal cast. Side view. X 1^. Same horizon, locality and 



collection. 20. 



6. Ditto. Ditto. X Ij. Same horizon, locality and collection. 20. 



7. Ditto. Sinus view. X 1|. Same horizon, locality and collection. 20. 



8. Ditto. Side view. X l^- Same horizon, locality and collection. 20. 

 8a. Dorsal view. X 1^. 



9. Oxydiscus ? llanvirueusis (Hicks). Side view of counterpart of type. 



Upper Arenig, Llanvirn. Sedgwick Mus. 22. 



10. Ditto. Side view. X 2. Llandeilo Beds, Abereiddy Bay, Mus. Pract. 



Geol. [28020]. 23. 



10 a Ornament. X 6. 



11. Ditto. Counterpart of fig. 10. x2. Mus. Pract. Geol. [28018]. 23. 

 11a. Ornament. X 6. 



12. Cyrtolltes bndleighensis, sp, nov. Internal cast. Side view. X 1 j. 



Ordovician Pebble, Budleigh Salterton. British Mus. [G. 15296]. 24. 

 12a. Dorsal view. X H- 12/>. Front view. X 1^. 



13. Ditto. Internal cast. Side view. X 1\. Same horizon, locality and 



collection [G. 15298]. 24. 



14. Ditto. Internal cast. Side view. X 1^. Same horizon, locality and 



collection [G. 15299]. 24. 



14a. Dorsal view. X 1\. 



15. GyrtoHfes craigensis, sp. nov. Internal cast. Side view. Nat. size. 



Stinchar Limestone, Craighead. Mrs. Gray's Coll. 24. 



15 a. Restored dorsal view. Nat. size. 



