PLATE 13. 
Figs. 1-5. Strophodonta patersoni.. 
1. A ventral valve, of medium size, and depressed convex form. 
2. A larger imperfect specimen, showing more distinctly the transverse wrinkles. 
3. A large individual in which the striae are not so strongly marked as in the other specimens. 
4. A cast of the ventral valve, showing the muscular impression, and preserving the marks of the 
exterior striae. 
5. A profile of fig. 3. 
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89 
Figs. 6 - 11. Strophodonta inequiradiata... . 87 
6. A ventral valve of an individual of medium size. 
7. A larger individual, having the cardinal extremities produced. 
8. A cast of a large ventral valve. 
9. A profile of fig. 8. 
10. The cast of a ventral valve of this species. 
11. An enlargement of the muscular impression of the same specimen. 
Figs. 12,18. Strophodonta hemispherica. 90 
12. A ventral valve of extremely gibbous form, from Poit Colborne, Canada West. 
13. A profile of the same. This specimen presents some variations from the usual form and 
character of those from New York and Ohio, which have been referred to this species. 
* 
