PLATE 81. 
Fig. 1. 351. 11. Modiolopsis modiolaris. (Pag. 294.) 
1 a. A specimen preserving the two valves in connection, showing the hinge-line, and the anterior muscular 
impression, which produces an elevation upon the outer surface of the shell. 
1 b. Another specimen preserving the two valves, which are laterally compressed. The anterior extremities 
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. 
1/. 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 nasutus. 
(Pag. 296.) 
Fig. 3. 
352. 
12 . 
Modiolopsis truncatus. 
(Pag. 296.) 
3 a. View of the right valve of this species. 
3 b. Profile view, one valve being more compressed than the other. 
Fig. 4. 353. 13. Modiolopsis ctjrta. 
A large individual of this species, from near Grimsby, Canada West. 
(Pag. 297.) 
Fig. 5. 354. 14. Modiolopsis ( Species undetermined). 
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.) 
(Pag. 297.) 
