PLATE 38 a. 
Page 
Figs. 1-22. Spirifera macronota. 281 
1-3. Dorsal, ventral and profile views of one of the smallest specimens which have been 
satisfactorily recognized as belonging to this species. 
4-6. Ventral, cardinal and profile views of a specimen of medium size, with a high area and 
stronger plications than is usual in the species. 
7 -10. Dorsal, front, ventral and cardinal views of a somewhat characteristic specimen. The 
dorsal valve has been slightly crushed, giving a little less rotundity to the shell than 
natural. 
11, 12. Ventral and cardinal views of a very characteristic ventral valve, showing the typically 
fine plications, shallow sinus, and vertical area. 
13. Cardinal view of a large individual, having a very high area, and preserving the covering of 
the foramen in place. The specimen is somewhat crushed, giving an appearance of 
greater rotundity to the dorsal valve than natural. 
14. View of a large dorsal valve possessing the characteristic form, with the fine plications. 
15. Cardinal view of specimen fig. 14, showing the high vertical area and narrow deltidium. 
16. Profile of specimen figs. 7 -10, contrasting somewhat with fig. 6, in the height of area and 
proportional depth of the valves. 
17. 18. Views of two characteristic dorsal valves, showing considerable variation in outline. 
19. Cardinal view of a ventral valve, showing a much lower area than figs. 5, 10, 12 and 15. 
This, and figures 10 and 15, show the callus within the foramen extending to varying 
distances from the apex in the different individuals. 
20. Interior of a dorsal valve, showing the dental sockets, cardinal process, and muscular impres- 
21. Interior of the ventral valve, fig. 19, showing the muscular impression and dental plates. 
22. Interior of a smaller ventral valve, showing muscular impression, dental lamellse, etc. 
