lO 



an excrescence, offers very little by way of suggestions to settle these 

 points. Yet some cases of unsilicified and apparently immature 

 examples give a hint. These taken with the newly observed 

 forms do go quite a little way in answering some of the questions. 

 ^S". rugosiun exhibits in growth a dome like mass, with fe\v fur- 

 rows or corrugations and with lamina above lamina. The con- 

 nection of the overlying lamina with that below is obscure, yet in 

 some cases there seem to exist pillars or tubes reaching from 

 below upward, though without uniform system. 



The mode of growth of the much later Stromatopora is very 

 suggestive as to the growth of Stroinatocerliim. Instead of pass- 

 age through tubes or hollow pillars (?) circulation through porous 

 calcareous stroma of the Stromaiocerhiin may have been possible. 



The weather worn sections of .S*. ^a/o//'/ indicate that the surface 

 of the living form bore close set eminences or mammillae, growth 

 taking place over and among these. See Plate LXXI. 



The S. laiuotiensc^ so far ;is observation has gone, had its 

 upper surface raised into a series of waves, a coarse ridgy growth. 

 This in cross section shows saw or sierra like projections as may 

 be seen in Plate LXX, lower figure. 



The relationship of these ancient animals is yet obscure. 

 While verging in some ways toward the coralline structure they 

 still seem to be holding to a sponge like form. Here among the 

 sponges, where so many uncertain species are provisionally con- 

 signed, the Stromatoceriuni may rest. 



Some suggestions are here offered as to the possible relationships 

 between the genus Stroinatocerhi?n and genera, both below and 

 above. While S. 7-ugosutn was regarded as the sole represen- 

 tative of a genus that appeared and disappeared with the Black 

 River, scarcely a hint could be expected. But from the discov- 

 ery of the species here recorded, which existed at lower horizons 

 and in far greater mass, it seems probable that S. riigosui7i was a 

 decadent or rapidly mutating form, the culnjination of the genus 

 passing with the species S. lamotteiise. 



If we now inquire as to like forms we shall see a general resem- 

 blance of the Stromatocerin/n to the Cryptozoon below and the 

 Stroviatopora above. The upper trend of life and development 



