EXPLANATION OF PLATE V. 



Page. 

 OltTIIIS RESUPINATA? 265 



Fig. 1. View of a dorsal valve, slij^htly exfoliated, but retaining the shell in great part. 

 2. A cast of a dorsal valve, showing the muscular imprint. 



Pkoductus elegans 268 



Figs. 3-4. Profile and front views of a specimen referred to this species. 



Productus semireticulatus •. 267 



Figs. 5-6. Vertical and cardinal views of a specimen referred to this species, showing the 

 form and surface character. 



Productus i-^vicostus ? 266 



Figs. 7-8. Vertical and front views of specimens having the form and character of the species. 



Productus Flkmingi var. Burungtonensis 265 



Fig. 9. View of a dorsal valve, showing the cardinal process. 



10. View of a ventral valve. 

 11-12. Front and profile views of a similar individual, presenting the features of those from 

 Burlington, Iowa. 



Spirifera striata 269 



Fig. 13. Dorsal view of a specimen somewhat crushed, hut showing the specific characters 

 of the shell. 



14. Ventral view of the same specimen. 



15. Ventral valve of another individual, showing fewer bifurcations in the plications. 



Spirifera sp. ? 271 



Fig. 16. View of the fragment referred to on page — . 



Spirifera setigera 270 



Fig. 17. View of a small specimen somewhat compressed, but preserving the surface char- 

 acters and somewhat the general form. 

 18. View of a larger dorsal valve, sbowiug the form. 



Atiiyris subquadrata ? ; • 271 



Fig. 19. View of the dorsal side of a specimen referred to this species. 



20. Ventral valve of the same, showing the sinus as well as the general form of the shell. 



