232 



MINERALS AND GEOLOGY 



cells, and convex tabulae, Fig 138. (6) Halysites (the "chain corals"), 

 with oval or round cell-tubes united in chain-like groupings, Fig. 139. 

 Syringopora, with round, reed-like cell-tubes, united by short trans- 

 verse tubes, Fig. 140. 



FIG. 136. 



a. Monticulipora (Stenopora or Choutetes) fibrosa ; b. M. petropolitana. Trenton 

 and Hudson River Formations. 



FIG. 137. 



Favosites Gothlandica. Silurian 

 and Devonian. 



FIG. 138. 



Michelinea contexa. 

 Devonian. 



FIG. 137* 



Aheolites cryptodens. 

 Devonian 



Halysites catenulatus. 

 Formation. 



FIG. 139. FIG. 140. FIG. 141. 



Niagara Syringopora Maclurea. S. Hisingeri. 



Devonian. Devonian. 



2. Tabulo-Stellata : Tabulae and radiating septa both present 

 No vesicular tissue, or traces merely. 



Both compound and simple forms are included in this section. 

 The more common Canadian genera comprise : (1) Columnaria Fig. 

 142, with compound corallum made up of hexagonal or polygonal 

 cell-tubes, with short septa and horizontal tabulae. Distinguish from 

 Favosites, which it much resembles in general aspect, by the border 

 of short radiating-septa at the cell-walls and the absence of pores ; 





