TAB. V. 



Fig. 12. Cythereis Lonsdaleiana. 



a X 50 Left valve, outside 

 5 X 50 Right valve, outside 

 c X 50 Right valve, dorsal edge 



Fig. 13. Cythereis cornuta. 



Adult, right valve, outside 



Young, left valve, outside . 

 ^ ^ ^K, Young, perfect, dorsal aspect 

 d X 50 Young, perfect, ventral aspect 

 e X 50 Young, perfect, anterior aspect . 



Fig. 14. Cythereis alata. 



Right valve, outside 

 Perfect, dorsal aspect 

 Perfect, ventral aspect 

 Perfect, anterior aspect 



« X 50 

 h X 50 

 c X 50 



Chalk. 



Detritus. 



Norwich. 



Charing. 



a 



X 



50 



b 



X 



50 



c 



X 



50 



d 



X 



50 



Chalk. 



Norwich. 



Fig. 1 5. Bairdia siibdeltoidea. 



a X 30 Perfect, dorsal aspect 

 5 X 30 Perfect, anterior aspect 

 Left valve, outside 

 Right valve, outside 

 Left valve, inside 

 Right valve, inside 

 Right valve, dorsal edge 

 Right valve, anterior edge . 

 Right valve, posterior edge 



c X 30 

 d X 2,0 

 e X 30 

 ./ X 

 f X 

 f'X 30 

 f'X 30 



30 

 30 



Detritus. 

 Chalk. 



Charing. 

 Gravesend. 



Fig. 16. Bairdia Siluiua. 



tt X 30 Perfect, dorsal aspect . 



^ X 30 Perfect, anterior aspect 



c X 30 Right valve, outside 



<^ X 30 Right valve, inside 



e X 30 Var. a, perfect, anterior aspect 



/ X 30 Var. a, perfect, obhquely placed, left valve 

 upwards ■ • • • 



ff X 30 Var. a, perfect, dorsal aspect 



h X 30 Var. j3, perfect, right valve upwards 



Detritus. 

 Chalk. 



Detritus. 



Charing. 



Gravesend. 



Charinof. 



