part 2] rugose corals from the burindi series. 171 



Discussion". 



Prof. H. L. Hawkins congratulated the Authors on the addition 

 of a fresh case to the growing volume of evidence regarding syn- 

 chronous parallelism in evolution. With respect to the hypertro- 

 phied columellae of the two new genera, he enquired whether there 

 was evidence to show reason for such a development. Voluminous 

 deposition of calcite was often a symptom of phylogerontic 

 stages, but seemed to be induced occasionally by environment. 

 Was the peculiarity of these corals to be ascribed to life in ' cal- 

 careous ' surroundings, or was it due to phyletic senility ? If the 

 latter were the explanation, it was peculiarly interesting to find 

 end-forms of such distinct lineages appearing at the same time in 

 the same district, while series of the same lineages were still 

 nourishing elsewhere. 



Dr. Stanley Smith replied that he considered that the excessive 

 deposition of calcite to form the columella was rather due to 

 phylogerontic reasons than to excess of calcium carbonate in the 

 sea. The conditions of deposition were not excessively calcareous, 

 rather the reverse. He pointed out, however, that the tissue other 

 than the columella was not particidarly thicker, as is often the 

 case where an organism shows more than usually a tendency to 

 deposit calcium carbonate. 



