PLATE 39. 



Page 

 Figs. 1 - 12. Spiripera l^vis 239 



1. View of a cast of a dorsal valve of a small individual. 



2. Cast of a ventral valve of a small individual, showing the muscular impression. 



3. Dorsal view of an imperfect specimen, showing the ventral area, and the deltidium in place. 



4. Cast of a dorsal valve of a large individual. 



5. Cardinal view of a ventral valve, showing the deltidium in place. 



6. Int<'rior of a ventral valve, showing the area, mnscular impression, with the deUidial plate. 



covering the upper part of the foramen. 



7. Exterior of a large ventral valve preserving the shell and showing a remarkably wide suban- 



giilar sinus, with obscure plications on the sides of the shell. 

 8-11. Cast* of ventral valves, showing considerable variation in the sise and proportions of 



the muscular impression. 

 12. Cardinal view of a cast of a ventral valve. 



