OUR COMMON BRITISH FOSSILS. 



walls in the hilly districts where Silurian, Devonian, 

 Carboniferous, or Oolitic limestone crops up, are often 

 composed of little else than blocks of fossil coral. 



We are beginning to understand the true relationship 

 of living and extinct corals better than we did, thanks 

 to the labours of Dr. Sorby, Professor M. Duncan, 

 and Professor H. N. Mosely. Formerly these animals 

 (classified chiefly by the stony or limy parts they leave 

 behind) were all grouped among that order of the 

 Actinozoa called Zoantharia, of which the common 



Fig. -^.Favosites Gothlandica: e, cluster of tubes of Favosites; d, tubes (magnified), 

 showing tabulae and perforations connecting the tubes. 



sea-anemone is a type. The order Zoantharia was 

 split up into three divisions, called Tabulata, Rugosa, 

 and Aporosa. It was thought the two former were 

 Palaeozoic types of corals, and the third of Neo- 

 zoic and Recent corals. Let us examine the funda- 

 mental difference of these three groups. The tabulate 

 corals are remarkable, and, indeed, obtain the name 

 which distinguishes them, for the partitions which 

 seem horizontally to split them up into chambers. 



