PLATE IV B— Continueil. 



DINOBOLUS, Hall. 



Page 36. 



DiNOBOLUS CONKADI, Hill I. 



Fig-. 13. An intenial cast of a brachial valve, indicating- very distinctly the muscular impressions and the 

 minute jilatform-vaults. 



Niagara limestone. Q-rafton, Wisconsin. 

 Fig. 14. An internal cast of a young pedicle-valve ; sho\ving the close ai)proximation of the platfonn-vaults. 



Niag-ara limestone. Near LeClaire, Iowa. 

 Fig. 15. An internal cast of a pedicle-valve ; indicating the duplicate platform- vaults. 



Niagara limestone. Racine, Wisconsin. 

 Fig. Iti. An intei-nal cast of a pedicle-valve in which the vaults of the platform attained unusual length. 

 Fig. 17. The counterpart of the same ; from a gutta-percha impression. 



Niagara limestone. Near LeClaire, Iowa, 

 Fig. 18. A transvei-se section of a shell near the anterior edge of the platform. 

 Fig. 19. An internal cast of the pedicle-valve, retaining very distinctly the median and lateral muscular 



seal's and the inipi-ession of the crescent. 

 Fig. 20. The counterpart of the same, from a gutta-percha impression ; showing the usual size and char- 

 acter of the deltidium. 



Niagara limestone. LeClaire, Iowa. 

 Fig. 21. The interior of a pedicle-valve, having the deltidium exti-emely developed. From a gutta-pei-cha 

 impression of a natui-al cast. 



Niagara limestone. Near LeClaire, Iowa. 

 Fig. 22. An internal cast of a brachial valve, the umbonal cavity of which has been filled by thickening of 

 the shell. 



Niagara limestone. LeClaire, Iowa. 

 Figi, .23. , Ap iij^ternal cast of a lai-ge brachial valve, with the muscular impressions sharply defined. 



Niagai-a limestone. Racine, Wi.^consin. 

 Fig. 24. An internal cast of a bi-achial valve ; showing the unsymmet'-ical development of the vaults of 

 platform, two on one side and three on the other. 

 Niagara limestone. LeClaire, Iowa. 



