THE HAMILTON ASSOCIATION. 1 25 



inse. In a few cases these are attached to ordinary laminae as a sort 

 of inner wall. The ordinary laminae in the more regular specimens 

 are often of great continuity, Extending without interruption for sev- 

 eral square inches. 



The above is an accurate description of the most common 

 type of stromatopora, when in its natural condition. I have a 

 specimen here which I obtained from the Clinton, about half-a-mile 

 east of the JoUey Cut. It is of parasitic growth incrusting a favosite ; 

 the entire form was some five inches in diameter, enclosing the 

 favosite all but the under side in a hemispherical form, thinning out 

 at the margins. It has been named by Professor J. W. Spencer, 

 Caunopora Walkerii. He describes it in the following manner : — 

 Laminse thin and obscure with chambers entirely filled with supple- 

 mental matter, only occasionally traversed by short, tortuous cana- 

 liculi, connected with the vertical tubes. Vertical pillars connecting 

 laminse removed or obscured by the filling, but with numerous con- 

 necting pores apparent and filled with matter different from the rest 

 of the mass. The organism is traversed by irregularly situated 

 tubes producing orifices on the surface of about one-half millimetre 

 diameter, and scattered over the surface from 2 to 4 mm. apart. 

 The connecting pores are crowded together, and are apparently 

 situated around centres, or sometimes around the larger tubes. 

 These tubes extend down into the substance and appear to traverse 

 several thicknesses of the laminse. I have chosen these two forms 

 described by Sir J. W. Dawson and Prof J. W. Spencer from the 

 fact that they are most divergent. Another form, Coenostroma 

 Antiquum, from the Niagara at Thorold, is an incrusting form, differ- 

 ing from all others of the class Coenostroma from the fact that each 

 group of tubulse is separated by a thin layer of clay before the next 

 was formed, showing that each group of tubulse was of separate and 

 independent growth ; in other respects it differs but httle from the 

 other forms of Coenostroma. 



I might mention that these forms are found in the Dolomite 

 limestone of Niagara and Guelph ; in fact these forms are almost 

 always associated with magnesian rocks, and are so abundant at 

 times as to make up certain layers. The study of these forms was 

 comparatively in its infancy until lately. I see that Prof Nicholson 

 and others have published a most elaborate work on these forms of 

 late, most carefully illustrated ; but as it is in connection with a 



