PLATE 8, 
1. Discina vanuxemi. 
1. Profile view 
1 a. Dorsal view, showing the form of the shell. 
1 b. Enlargement of surface, showing the radiating and concentric stria; (the latter are not 
strong enough in proportion to the others). 
2 - 1G. Stropiiodonta varistriata. 
2 - G. Ventral valves, where the striae are nearly equal or alternating in size. 
7 & 8. Individuals presenting some variety in surface characters. 
9. A young shell with salient hinge extremities, and strongly elevated stria; separated by 
fascicles of liner stria; between. 
5 a. The upper figure with this number is an enlargement of the surface of fig. 9. 
10. An individual with surface characters similar to the last, having the binge extremities 
rounded, and the hinge line a little shorter than the greatest width of the shell below. 
11. Interior of' a ventral valve. 
11 a ( by error 12 a) above last figure. An enlargement of the area and crenulations. 
12 & 12 a. Interior of ventral valve, and enlargement of area. 
13. Interior of a ventral valve. 
14 & 10. Casts of the interior of the ventral valve, where the shell is but partially exfoliated. 
15 & 15 a. The interior of a ventral valve, and enlargement of a portion of the same. 
1G, at right hand of page. A portion of the surface much enlarged, showing the nearly equal 
striae crossed by finer concentric lines. 
17 - 23. Spirifer vanuxemi. 
17, 18 & 19. Young individuals of this species. 
20. Dorsal view of a medium-sized specimen. 
20 a, b, c. Ventral, profile and front views of the preceding specimen. 
21 & 23. Dorsal views of larger specimens. 
22. Ventral view of another specimen of this species. 
23 a. Enlargement of the surface, showing the concentric lamella;. 
