PLATE VI. 



Fig. I. ()utline of a specimen oi Monticitlipiva {Hctcrotrypa) i)ia)iuiiulafa, D'Orb., 



from the Cincimiati group of Ohio, of the natural size. 

 Fig. I a. Portion of the surface of a specimen of the same, showing very faintl) 



marked monticules, of the natural size. 

 Fig. I b. Portion of the surface of another specimen of the same, showing more 



conspicuous tubercles, of the natural size. 

 Fig. I I. Surface of the same, enlarged eighteen times. 

 Fig. I d. Tangential section of the same, taken just below the surface, showing 



the larger and smaller tubes, and the occasional hollow spines, (spiniform 



corallites). 

 Fig. 1 c. Part of the same section, enlarged fifty times. 

 Fig. \ f. Another tangential section, taken at a deeper le\'el than the preceding, 



enlarged twenty times. 

 Fig. I g. Portion of a vertical section of the same at right angles to its flat sur 



faces, enlarged eighteen times, showing the different tabulation of the larger 



and smaller tubes. 

 Fig. 2. A specimen oi Mo7itlcuUpora {Peronopora) molesta, Nich., from the Cincin- 

 nati group of Ohio, of the natural size, showing the well-marked mt)nticules. 

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

 Fig. 2 b. Tangential section of the same, enlarged eighteen times, showing the 



large and small corallites, and imperfect tabulae of the former. 

 Fig. 2 c. Part of the preceding section, enlarged fifty times. 

 Fig. 2 d. Part of a vertical section of the same, showing the close tabulation of 



tlie small corallites, and the incomj)lete tabula of most of the large tubes. 

 Fig 3. A specimen oi MonticuUpoi-a {Moiiotrypd) pavouia, D'Orb. ( = M. dafhra- 



tula, James), from the Cincinnati group of Ohio, of the natural size. 

 F'ig. 3 a. Portion of the surface of the same, enlarged eighteen times. 



