PLATE IV. 



Fig. I. A specimen of Moiiticulipora {Prasopora) Newberry i, Nich., from the 



Cincinnati group of Ohio, viewed from above, of the natural size. The 



thin corallum is fractured in various directions. 

 Fig. I a. View of the margin of the same, of the natural size, showing the 



thickness of the corallum. 

 Fig. I b. Part of the surface of the same, enlarged eighteen times. 

 Fig. I c. Tangential section of the same, enlarged eighteen times, showing the 



two kinds of corallites, and the incomplete tabulse of the large tubes. 

 Fig. I d. Part of the preceding section, enlarged fifty times. 

 Fig. I e. Vertical section, enlarged eighteen times, embracing the entire thick- 

 ness of the corallum, and showing the different tabulation of the larger and 



smaller corallites. 

 Fig. 2. Outline of a portion of an Orthoceras covered by a colony oi Monticuli- 



pora {Monotrypa) tuberciilata, Edw. and Haime (= M. corticans, Nich.), of 



the natural size, showing the form of the elongated tubercles. From the 



Cincinnati group of Ohio. 

 Fig. 2 a. Part of the surface of the same, enlarged eighteen times. 

 Fig. 2 b. Part of a tangential section of the same, enlarged eighteen times. 

 Fig. 2 c. Small portion of the preceding section, enlarged fifty times, showing 



the structure of the wall. 

 Fig. 3. A specimen of MoJiticidipora {Monotrypd) discoidea, James, viewed from 



above, of the natural size. From the Cincinnati group of Ohio. 

 Fig. 3 a. Under side of the same specimen, showing the basal epitheca. 

 Fig. 3 b. Side-view of the same, showing the thickness of the corallum. 

 Fig. 3 c. Tangential section of the same, enlarged eighteen times, showing the 



hollow spines (spiniform corallites) at the angles of the ordinary tubes. 

 Fig. 3 d. Part of the preceding section, enlarged fifty times. 

 Fig. 3 e. Part of a vertical section, of the natural size, embracing the whole 



thickness of the corallum. 

 Fig. 3 / A single tube from the preceding section, enlarged fifty times, showing 



the structure of the wall. 

 Fig. 4. A specimen of Monticidipora {Diplotiypd) calycula, James, of the natural 



size, from the Cincinnati group of Ohio. The surface bearing the calices 

 • is buried in the matrix, and all that is seen is the deeply concave basal 



epitheca. 

 Fig. 4 a. Tangential section of the same, enlarged eighteen times. 

 Fig. 4 b. Vertical section of the same, embracing the whole thickness of the 



corallum, enlarged eighteen times. 



