FOSSIL CORALS. 83 



species have been enumerated from this formation 

 alone ! 



These numbers, however, do not convey to the 

 mind of the student such a clear idea of the relative 

 abundance of fossil corals in the older rocks, as he 

 can get for himself by geologizing in two or three 

 localities where corals are abundant. 



Mr. Etheridge thinks that during no period in the 

 physical history of the British Isles has there been 

 such a remarkable assemblage of corals as when the 

 Middle Devonian rocks of North and South Devon 

 were formed. Out of fifty-two species not one passes 

 to the Carboniferous formation, and none are common 

 to the Silurian rocks of any area. The limestones of 

 Torquay and Newton Abbot are simply Devonian 

 coral-reefs of great magnitude. 



Some splendid geologizing may be obtained in the 

 neighbourhood of Girvan, in Ayrshire a rather com- 

 plicated tract of Upper Silurian rocks. The district 

 is a pleasant one to work in, with the Atlantic on 

 one side, and the hilly sheep-pastures on the other. 

 Numerous quarries may be found, and pleasant little 

 adventures made along miniature gorges cut by 

 the "burns," where we hammer at the rocks which 

 crop out. Within six or seven miles of Girvan there 

 are at least forty good fossilizing spots. The best 

 of them is Woodland Point an exceedingly rich 

 treasure-house of Silurian fossils. Here many corals 

 may be collected, such as Heliolites, Plasmopora, 



