PLATE XV. 



Fig. I. Fragment oi Dekayia attrita, Nich., from the Cincinnati Group of Ohio, 

 of the natural size. 



Fig, I a. Portion of the surface of the same, enlarged. 



Fig. I /'. Tangential section of the same, enlarged twenty times, showing the 

 spiniform corallites scattered among the ordinary tubes. 



Fig. I c. Vertical section of the same, enlarged twenty times, showing the 

 characters of the two sets of corallites just before they open on the 

 surface. 



Fig. 2. A small specimen of Fistulipora {Callopora) proporoides, Nich., from 

 the Hamilton Group of Canandaigua, State of New York, of the natural 

 size. 



Fig. 2 a. Part of the surface of the same, enlarged. The large circular tubes 

 have projecting and open calices, but the mouths of the interstitial angular 

 tubes are mostly closed by a calcareous membrane, and the lines of divi- 

 sion between them are only faintly indicated. 



Fig. 3. Part of the surface ol Fisiidipora {Cal/opora) hurassata, Nich., from the 

 Hamilton Group of Arkona, Ontario, enlarged. The mouths of the in- 

 terstitial corallites are seen in the specimen figured ; but they are often 

 concealed from view by a calcareous membrane. 



Fig. 3 a. Part of a tangential section of the same, enlarged twenty times, 

 showing the oval corallites with a slight constriction on one side, sur- 

 rounded by a series of angular corallites. 



Fig. 3 /'. Part of a vertical section of the same, enlarged twenty times, showing 

 the remotely-tabulate oval tubes, and the vesicular tabute of the angular 

 corallites. 



Fig. 4. Part of a tangential section of Labcchia coiiferta, E. and H., from the 

 Wenlock Limestone of Benthall Edge, enlarged ten times, showing the 

 primitively tubular condition of the pillars, and the transversely-divided 

 edges of some of the vesicular tabulae. 



Fig. 4 a. Part of the upper surface of another specimen of the same, from the 

 same locality, enlarged. The surface-tubercles in the specimen figured 

 are more extensively confluent than is usually the case. 



