CONTEMPOEAEIES AND SUCCESSOES OP EOZOON. 165 



NOTE TO CHAPTER VI. 

 A. STROMATOPORID^E, ETC. 



For the best description of Archaeocyathus, I may refer to 

 The Palaeozoic Fossils of Canada, by Mr. Billings, vol. i. 

 There also, and in Mr. Salter's memoir in The Decades of the 

 Canadian Survey, will be found all that is known of the struc- 

 ture of Eeceptaculites. For the American Stromatoporsa I 

 may refer to Winchell's paper in the Proceedings of the 

 American Association, 1866 ; to Professor Hall's Descriptions 

 of New Species of Fossils from Iowa, Report of the State 

 Cabinet, Albany, 1872 ; and to the Descriptions of Canadian 

 Species by Dr. Nicholson, in his Report on the Palaeontology 

 of Ontario, 1874. 



The genus Stromatopora of G-oldf uss was denned by him as 

 consisting of laminae of a solid and porous character, alternat- 

 ing and contiguous, and constituting a hemispherical or sub- 

 globose mass. In this definition, the porous strata are 

 really those of the fossil, the alternating solid strata being the 

 stony filling of the chambers ; and the descriptions of subse- 

 quent authors have varied according as, from the state of 

 preservation of the specimens or other circumstances, the 

 original laminae or the filling of the spaces attracted their 

 attention. In the former case the fossil could be described as 

 consisting of laminae made up of interlaced fibrils of calcite, 

 radiating from vertical pillars which connect the laminse. In 

 the latter case, the laminae appear as solid plates, separated by 

 very narrow spaces, and perforated with round vertical holes 

 representing the connecting pillars. These Stromatoporse 

 range from the Lower Silurian to the Devonian, inclusive, and 

 many species have been described ; but their limits are not 

 very definite, though there are undoubtedly remarkable dif- 

 ferences in the distances of the laminae and in their texture, and 

 in the smooth or mammillated character of the masses. Hall's 

 genus Stromatocerium belongs to these forms, and D'Orbigny's 

 genus Sparsispongia refers to mammillated species, sometimes 

 with apparent oscula. 



