70 OUR COMMON BRITISH FOSSILS. 



Indian seas, where it is met with in coral-reefs, and 

 masking and adhering to natural rocks. Astrcea 

 favosa (Fig. 51), on the other hand, is peculiar to the 

 East Indian seas, where it is hardly less abundant. 

 Astraa ananas (Fig. 52) is a common fossil in the 

 Silurian limestone at the Wren's Nest, Dudley, in the 

 formation of which we can hardly doubt that it and 



Fig. 53. Lithostrotion basaltiforme, an abundant compound Rugose Coral in the 

 Carboniferous limestone. The lighter parts show the transverse structure, as 

 seen when the coral is cut for sections. 



its compeers took a considerable part. For Professor 

 Owen tells us that the Wenlock Edge, in Shropshire, 

 belonging to the same formation, is nothing more or 

 less than an ancient coral-reef thirty miles in length ! 

 The Plymouth limestone belongs to the Devonian 

 period, and in it we find this and other genera of reef- 

 building corals ; and many of our best palaeontologists 



