I'LATH LV. 



Genus — OsTKEA, Lin lunas. 

 Figs. 



1 — 3. 0. JValkt^ri, Keep. Lower Greeiisand, Upwaiv. Sedgwick Museum, 

 Cambridge. (P. 360.) 



1 . The Tvpe. a , right valve ; h, left valve ; c, anterior view. 

 2, 3. Interiors of left valves. 



4 — 9. 0. vesicidaris, Lam. (P. oGO.) 



4. Probably zone of flb/rts^e;- j^/(i««s, S waff haul, Norfolk. Norwich Museum, 



No. 3290. Young individual attached to Micraglev. Eight valve and 

 portion of left valve. 



5. Gault, Folkestone. Sedgwick Museum. », right valve; 6, anterior view 



showing left valve almost entirely attached to a flat portion of Inoceramns. 



6. Zone of Belemnitella mucronata, Norwich. Dr. Eowe's Collection. Attached 



obliquely to a BdemniteUa. a, right valve; h, anterior view. 



7. Zone of Actinocama,c qttadralus, East Harnham. Dr. Blackmore's Collec- 



tion. ((, right valve ; li, anterior view showing the hirger part of the left 

 valve attached to a flat Iiiucvvaiitus. 

 8, 9. Zone of Hvlaster )-iih(jlulot<ii>', Blue Bell Hill, Burhani. British Museum, 

 Nos. L 10408, L 10409. 8, 9a, left valves ; 9b, dorsal view of da, showing 

 the small surface of attachment. 



10 — 14. 0. vesiculosa (Sow.) Upper Greensand. Left vah-es. (P. 374.) 



10. Zone of Pec/ew as/)er, Ballai'd Down. Sedgwick Museum, fc, posterior view. 



11. Zone of Pecien asjjer, Warminster. Museum of Practical Geology, 



No. 26942. 



12. Zone of Schlcenhachia rostrata, Isle of Wight. Same museum, No. 25936. 



li, posterior view. 



13. Zone of HcMcenhachia rostrata, Potlerne. Same uuiseum, No. 26932, 



b, posterior view. 



14. Zone of Schlcenhachia rostrata, Dintou. Same museum, No. 25938. 



b, posterior; c, interior. 



