PLATE IV u— Coutinueil. 



DINOBOLUS, Hall. 



Page 36. 



DiNOBOLUS CONRADI, Hilll. 



Fig-. 13. An internal cast of a 'brHchial valve, indicating vei-y distinctly the mu.scular imiiression.s .hmiI the 

 minute platform-vanlts. 



Niagara limestone. Grafton, Wiscoiisin. 

 Fig. 14. An internal cast of a young pedicle-valve ; showing the close ai)pi-oximation of the platform-vaults. 



Niagara limestone. Near LeClaire. Iowa. 

 Fig. 15. An internal cast of a pedicle-valve ; indicaling the duj)licate platforni-vault.«. 



Niagara limestone. Racine, Wisconsin. 

 Fig. It). An internal cast of a pedicle-valve in which the vaults of the platform attained unu.sual length. 

 Fig. 17. The counterpart of the same ; from a gutta-percha impre.'i.sion. 



Niagai-a limestone. Near LeClaire, Iowa, 

 Fig. 18. A transverse section of a shell near the anterior edge of the platform. 



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

 scars and the impression 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. Theintenor of a pedicle-valve, having the deltidium extremely developed. From a gntta-percha 

 impres.«ion (if a natural cast. 



Niagara limestone. Near LeClaire, Iowa. 

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

 the shell. 



Niagara limestone. LeClaire, Iowa. 

 Fig. 23. An internal cast of a large brachial valve, with the muscular impressions shaiply dctiued. 



Niagara limestone. Batine, Wlivonsin. 

 Fig. 24. An iuternjU cast of a bi-achial valve ; showing the unsymuietrical development of the vaults of 

 |)latform, two on one .side and three on the other. 

 Niagara limestone. LeClaire, Iowa. 



