PLATE 81. 



Fig. 1. 351. 11. MoDioLopsis H0DI0LASI8. (Pag. 294.) 



1 o. A specimen preserving the two valves in connection, shovring the hinge-line, and the anterior muscular 

 impression, which produces an elevation upon the outer surface of the shell. 



I b. Another specimen preserving the two valves, which are laterally compressed. The anterior extremitiea 

 are narrowed, and somewhat obtusely pointed. 



1 c. A single valve, with the posterior extremity more regularly rounded, and the hinge-line curved. 



1 d. A smaller and shorter specimen, with the base not contracted or arched. 



1 e. A small specimen, contracted at the anterior, and expanded towards the posterior extremity. The base is 

 arched, and the hinge-line apparently curved. 



If. A specimen from the shales at Madison (Indiana), preserving both valves. 



1 g. The anterior extremity of a cast of this species, showing the prominence of the muscular impression. 



Fig. 2. 203. 4. MoDioLOPsis NA80TTTS. (Pag. 296.) 



Fig. 3. 362. 12. Modiolopsis teuncatus. (Pag- 296.) 



3 a. View of the right valre of this species. 

 3 b. Profile view, one valve being more compressed than the other. 



Fig. 4. 363. 13. Modiolopsis cueta. ( Pag. 297.) 



A large individual of this species, from near Grimsby, Canada West. 



Fig. 6. 354. 14. MomohOTBie {Species undetermined). (Pag. 297.) 



5 a. Left valve of the fragment. 5 b. Dorsal view of the same. 



(This species is erroneously marked 4 a, b, on some of the plates.) 



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