PLATE 37. 
MICHELINIA FAVOSITOIDEA. Devonian. 
Upper surface of a corallum from the blue clay of the Middle Devonian 
Falls of the Ohio. Collection of the author. 
[Norr.—With a lens of low power observe the papillose surface of the tabule and of the walls, the 
latter dotting the longitudinal ridges. The author recommends the use of a double-convex lens, with 
a power of about two diameters, in examining all the illustrations of this work. Viewed with such 
a lens, all characteristic structural details will appear as they seem in the fossil itself, and “an atmos- 
phere” so invests the figure that it may be studied almost as advantageously as the natural object.] 
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