168 



The Corals of the English Crag may belong to this period. 

 At one time it was believed that the Crag was very rich in 

 Corals, and one division of this formation was called Coralline, 

 from the supposed abundance of Corals therein. A careful 

 study of these fossils, however, has shewn that it is the 

 PoLTzoA, and not the Zoantharia, that abound. True Corals 

 are very rare in the Enghsh Crag, and still more so in its 

 equivalent formation at Antwerp. The Crag Corals belong to 

 four distinct genera, each of which is represented by different 

 species in other Meiocene formations ; three of the genera have 

 living representatives in our present seas, but none of them 

 have been found in the secondary rocks. 



The Pleiocene formations have no representative in the 

 British Islands, unless the Crag may turn out to be of that age. 

 They consist of the sub-Apennine strata found reposing on the 

 secondary rocks along the shores of the Adriatic and the 

 Mediterranean, and the newer formations of the same period in 

 Sicily. 



Many genera of Actinozoa have species living in our modem 

 seas; the recent, however, are all distinct from the Tertiary 

 species. In the foUowing table I have given a Ust of those 

 genera only which are extinct and special to the Tertiaries. 



