TAB. I. 



Fig. 1. Cythere Hilseana. 



ffl X 50 Left valve, outside . . . Detritus. 



^ X 50 Right valve, outside 



c X 50 Right valve, inside . . , Gault. 



c XlOO Right valve, hinge 



c" X 50 Right valve, dorsal edge 



c"'X 50 Right valve, ventral edge . 



</ X 50 Left valve, inside 



d' X 100 Left valve, hinge 



e X 50 Right valve, outside 



e X 1 00 Punctations (of fig. 1 e) . 



/ X 50 Perfect carapace, anterior aspect 



^ X 50 Perfect carapace, dorsal aspect, seen obliquely 



Fig. 2. Cythere punctahda. 



« X 50 Old, perfect, dorsal aspect 



3 X 50 Old, left valve, outside 



c X 50 Immature, right valve, outside 



c? X 50 Immature, right valve, inside 



cT X 50 Immature, right valve, dorsal edge 



e X 50 Old, left valve, inside 



e X 50 Old, left valve, dorsal edge 



/ X 50 Young, right valve, outside 



/' X 100 Young, central surface (of fig. 2/) 



g XlOO Immature, central surface . 



h X 100 Immature, central surface 



i X 100 Old, central surface 



j X 50 Worn, perfect, left valve upwards 



>?: X 50 Immature, perfect, dorsal aspect 



/ X 50 Old, perfect, ventral aspect 



m X 50 Old, perfect, anterior aspect 



^ X 50 Var. virginea, perfect carapace, placed 

 obliquely, right valve upwards 



Charing. 

 Folkstone. 



Detritus. Charing. 



Greensand. 

 Gault. 



Warminster. 

 Folkstone. 



Detritus. 



Greensand. 



Gault. 



Detritus. 



Gault. 



Leacon Hill. 

 Folkstone. 



Charing. 



Warminster. 



Folkstone. 



Charing. 

 Folkstone. 



Chalk. Gravesend. 



