PLATE 9. 
Page 
Fig. 1 & 2. Lingula centrilineata. 155 
1. A small individual of this species. 
2. A larger specimen of the same. 
Fig. 3, 4 & 5. Lingula perlata. 156 
4. An individual of medium size, preserving the two valves. The outer shell is partially ex¬ 
foliated from the central part of the valve, 
8. Profile of the same specimen, showing the convexity of the valves. 
5. The lower part of a larger valve having the stria; more distant, very thin and sharply 
elevated, while towards the margin they are more closely arranged. 
5 a. Enlargement of the concentric lamellae. 
Fig. 6 & 8. Lingula rectilater^ . 156 
G. An individual of medium size. 
8. A large Individual of the same species. 
Fig. 7, 9 & 11. Lingula spathata. 157 
9. A large individual having the upper part of the shell broken off. 
7 & 11. Two views of a specimen having the base broken off. The convexity of the two valves 
is more than one-third the greatest width of the shell. 
Fig. 10. Lingula spatiosa. 158 
10. The shell, natural size. 
10 a. A portion of the surface enlarged. 
Fig. 13 - 15, & 16 a. Discina discus. 195 
13. The lower valve partially exfoliated, and showing radiating striae. 
14. Interior of the lower or ventral valve, showing the lainellose structure and radiating striae. 
[ In the figure the striae are too regular, and should be represented as bifurcating to¬ 
wards the margin.] 
13. A lower valve (with the margins slightly exfoliated ), preserving nearly entire the con¬ 
centric lamellose striae. 
16 a ( Error for 15 a). Profile of the lower valve, showing the convexity. 
15 6. Enlargement of the lamellose striae. 
15 a ( Error for 14 a). Enlargement of the radiating striae of fig. 14. 
Fig. 12, 16 & 17. Discina conradi. 161 
12 Exterior view of the lower valve (improperly represented without the foramen). 
12 a. Enlargement of the surface of the same. 
16. Dorsal valve having the outer shell exfoliated, and showing radiating striae which bifurcate 
towards the margins. 
17. Enlargement of the striae. 
17 a. Profile view of the dorsal valve. 
