PLATE X. 



Genus — Aucella, Keyserling. 



FIGS. 



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

 Museum. (The specimens figured Ijy Pavlow.) 1 (i, left valve ; 



1 /', anterior view ; 1 c, riglit valve. 2 a, left valve ; 2 h, right valve ; 



2 c, postex'ior view. (P. GO.) 



3 — 5. A. Kei/serUiuji(uiii, Trautsch. Claxby Ironstone, Claxby. Sedgwick 

 Museum. 3 */, left valve; 3 &, right valve; 3 r, posterior view; 3 J, 

 anterior ear and umbo of right valve X 3. 4 a, left valve ; -i //, right 

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



GemiS — AucELLiNA, Pomjpechj. 



G — 13. ^1. tjrijphseoides (Sow.). Cambridge Greensand, except figs. 11, 12, 13. 

 Sedgwick Museum. (P 72.) 



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



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



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



9. a, umbo and anterior ear of left valve x 3 ; 6, 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 Ij. 



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



13. Red Limestone, Speeton. Left valve. 



Geiins — Gekvili.iA; Def ranee. 



14 — IG. G. suhlanceolatd (d'Orl:).). Lower Greensand (Crackers), Atherfield. 

 Sedgwick Museum. (P. 74.) 



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. 



