Fig. 
] 
i) 
Or 
. Arca tetragona, page 76. 
a. outside view of specimen from 
Red Crag. 
6. inside view of the same. 
c. outside of abraded specimen, 
with a sinuated form of ven- 
tral margin (Bissoarca). 
d. inside of var. Britannica. 
. Arca lactea, p. 78. 
a. outside, left valve. 
4. inside of the same. 
. Arca pectunculoides, p. 79. 
a. outside of var. brevis. 
6. inside of var. elongata. 
. Nucinella miliaris, p. 73. 
a. inside of right valve. 
6. inside of left valve. 
ce. united valves, showing the posi- 
tion of the ligament. 
. Nucula tenuis, p. 84. 
6. Nucula nucleus, p. 85. 
10. 
Wale 
. Nucula trigonula, p. 86. 
. Nucula levigata, p. 81. 
. Nucula Cobboldiz, p. 82. 
Leda semistriata, p. 91. 
Leda pygmea, p. 95. 
a. inside view of an acuminated 
specimen. 
6. outside of a specimen of a 
more rounded form. 
. Leda caudata, p. 92. 
. Leda pernula, p. 93. 
. Leda truncata, p. 94. 
. Leda Thracizformis, p. 96. 
. Leda lanceolata, p. 88. 
. Leda myalis, p. 90. 
c. outside view of elongated var. 
The lines indicate the size of the specimens. 
