Polytremacis ami the Ancestry of the Helioporidce. 19 



Temperatux'e. 



Tapoiir-density. 



Observer. 



Remarks. 



About 1570°. . . 

 " (445°)' 



53 



80 to 52*6 

 63 -4 to 64 -7 

 (75 "7 instead of 

 normal) 



y. Meyer and 

 Ztiblin 



Crafts 



>5 



Nascent bromine from 



PtBr4. 

 Free bromine. 



(To show the accuracy 

 attained.) 



It should be noted that in all these experiments the bromine Avas 

 mixed with an indeterminate quantity of air, which makes them hardly 

 comparable with our results. 



Polytremacis and the Ancestry of the Helioporidte." By J. W. 

 Gregoey, D.Sc. Communicated by Professor Lankester, 

 F.Pt.S. Eeceived November 21— Read December 7, 1899. 



(Abstract.) 



The recent blue coral Heliopora presents striking resemblances in 

 structure to the palseozoic Heliolites. All the earlier writers on corals 

 ^accordingly regarded the two genera as intimately allied. But some 

 later authorities consider the resemblances as accidental, and that the 

 corals have no special affinities. Thus, according to F. Bernard, 

 Heliopora and Heliolites belong to distinct subphyla. Lindstrom admits 

 only one species of Heliojjora, and regards the genus as quite isolated, 

 .as essentially distinct in structure from Heliolites, and as further 

 separated from the latter by " the total absence of all connecting links 

 from the end of the middle Devonian to the recent times." The author, 

 however, considers that the original view of the close affinity of 

 Heliojjora and Heliolites is correct, that the two genera are essentially 

 •similar in structure, and that they are linked by a series of eocene 

 and cretaceous corals. Amongst these fossils is the genus Polytremacis, 

 which is redescribed, and a new species of Heliopora from the Cretaceous 

 of Somaliland. It is suggested that Heliopora has descended from the 

 palaeozoic Heliolitidse by degeneration in size and increase in number 

 of the coenenchymal cseca. 



