TAB. V. 
Fig. 12. Cythereis Lonsdaleiana. 
a X 
50 
Left valve, outside 
Chalk. 
Norwich. 
h X 
50 
Right valve, outside 
77 
c X 
50 
Right valve, dorsal edge 
77 
Fig. 13. Cythereis cornuta. 
a X 
50 
Adult, right valve, outside 
Detritus. 
Charing. 
h X 
50 
Young, left valve, outside . 
)) 
77 
c X 
50 
Young, perfect, dorsal aspect 
77 
d X 
50 
Y^oung, perfect, ventral aspect 
77 
e X 
50 
Young, perfect, anterior aspect . 
5? 
77 
Fig. 14. Cythereis cdata. 
a X 
50 
Right valve, outside 
Chalk. 
Norwich. 
h X 
50 
Perfect, dorsal aspect 
7) 
77 
c X 
50 
Perfect, ventral aspect 
77 
77 
d X 
50 
Perfect, anterior aspect . 
77 
77 ' 
Fig. 1 5. Bairdia suhdeltoidea. 
a X 
30 
Perfect, dorsal aspect 
Detritus. 
Charing. 
^ X 
30 
Perfect, anterior aspect 
77 
77 
c X 
30 
Left valve, outside 
Chalk. 
Gravesend. 
d X 
30 
Right valve, outside 
77 
77 
e X 
30 
Left valve, inside 
77 
77 
/ X 
30 
Right valve, inside . ■ . . 
77 
77 
/ X 
30 
Right valve, dorsal edge 
79 
77 
/'X 
30 
Right valve, anterior edge . 
77 
77 
/"X 
30 
Right valve, posterior edge 
77 
77 
Fig. 16. Bairdia Siliqud. 
a X 
30 
Perfect, dorsal aspect ... 
Detritus. 
Charing. 
^ X 
30 
Perfect, anterior aspect 
77 
77 
c X 
30 
Right valve, outside 
Chalk. 
Gravesend. 
X 
30 
Right valve, inside 
77 
77 
e X 
30 
Var. a, perfect, anterior aspect 
Detritus. 
Charing. 
/ X 
30 
Vaf. a, perfect, obliquely placed, left valve 
upwards . . . . 
77 
77 
y X 
30 
Var. a, perfect, dorsal aspect 
7 7 
77 
h X 
30 
Var. /3, perfect, right valve upwards 
77 
77 
