PLATE 38 A. 



Page 



Figs. 1 - 22. Spiripera macronota 231 



'1-8. Dorsal, ventral and profile views of one of the smallest 8])ccimeus which liave been 



satisfactorily recognized as belonging to this siwcies. 

 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. Tlie 



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. 0. in the Iieight 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 1-5. 



This, and figures 10 and 15, show the callus within the foramen extending to varying 

 distances from the apex in the diflTcrent individuals. 



20. Interior of a dorsal valve, showing the dental sockets, cardinal process, and muscular impres- 



sion. 



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 lamelln, etc. 



