FIGS. 



PLATE X. 



Genus — Aucella, Keyserling. 



1, 2. A. volgensis, Lahus. Spilsby Sandstone, Donnington. Sedgwick 

 Museum. (The specimens figured by Pavlow.) 1 a, left valve ; 



1 b, anterior view ; 1 c, right valve. 2 a, left valve ; 2 b, right valve ; 



2 c, posterior view. (P. 69.) 



3 — 5. A. Keyserlingiana, Trautsch. Claxby Ironstone, Claxby. Sedgwick 

 Museum. 3 a, left valve ; 3 b, right valve ; 3 c, posterior view ; 3 <1, 

 anterior ea,r and umbo of right valve X 3. 4 a, left valve; 4 b, right 

 valve. 5, left valve. (P. 70.) 



Genus — Aucellina, Pompeckj. 



6 — 13. A. gryphseoides (Sow.). Cambridge Greensand, except figs. 11, 12, 13. 

 Sedgwick Museum. (P 72.) 



6. a, left valve ; b, posterior view ; c, right valve ; d, part of right valve x 4. 



7. a, left valve ; b, right valve ; c, dorsal view. 



8. a, left valve ; b, right valve. 



9. a, umbo and anterior ear of left valve x 3 ; b, dorsal view showing areas, etc. 



x 3 ; c, area of right valve x 3. 



10. Anterior ear of right valve X 3. 



11. Lower Chalk, near Cambridge. Eight valve x 1£. 



12. Lower Chalk, Reach. Portion near the middle of the right valve x 6. 



13. Eed Limestone, Speeton. Left valve. 



Genus — Gteevillia, Def ranee. 



14 — 1G. G. sublanceolata (d'Orb.). Lower Greensand (Crackers), Atherfield. 

 Sedgwick Museum. (P. 7L) 



14. Eight valve of a young individual. 



15. Left valve of a young individual with only three ligament pits. 



16. Left valve of an immature specimen. 



