PLATE LV. 



Genus — Osteea, Linnaeus. 

 Figs. 



1 — 3. 0. Walkeri, Keep. Lower Greensand, Upware. Sedgwick Museum, 

 Cambridge. (P. 360.) 



1. The Type, a, right valve; b, left valve ; c, anterior view. 

 2, 3. Interiors of left valves. 



4 — 9. 0. vesicularis, Lam. (P. 300.) 



4. Probably zone of Holaster planus, Swaffhain, Norfolk. Norwich Museum, 



No. 3290. Young individual attached to Micraster. Right valve and 

 portion of left valve. 



5. G-ault, Folkestone. Sedgwick Museum, a, right valve; b, anterior view 



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



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



obliquely to a Belemnitella. a, right valve; b, anterior view. 



7. Zone of Act in oca mas quadratus, East Harnham. Dr. Blackmore's Collec- 



tion, a, right valve ; b, anterior view showing the larger part of the left 

 valve attached to a flat Inoceram us. 

 8, 9. Zone of Holaster subglobosus, Blue Bell Hill, Burham. British Museum, 

 Nos. L 10408, L 10409. 8, 9a, left valves ; 96, dorsal view of 9a, showing 

 the small surface of attachment. 



10 — 14. 0. vesiculosa (Sow.) Upper Greensand. Left valves. (P. 374.) 



10. Zone of Pecten asper, Ballard Down. Sedgwick Museum, b, posterior view. 



11. Zone of Pecten asper, Warminster. Museum of Practical Geology, 



No. 25942. 



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



b, posterior view. 



13. Zone of Schlcenbachia rostrata, Potterne. Same museum, No. 25932, 



b, posterior view. 



14. Zone of Schlcenbachia rostrata, Dinton. Same museum, No. 25938. 



b, posterior ; c, interior. 



