FOSSIL CORALLINES. 53 



Graptolites may be looked for with every prospect of 

 their discovery. 



The black shales at Garth, near Portmadoc, which 

 belong to the Upper Arenig rocks, are in places 

 crowded with Graptolites. The richest locality in 

 South Wales is perhaps Ramsey Island, where, in the 

 dark shales forming the cliffs, there are plenty of Phyl- 

 lograptus, Callograptus, Ptilograptus, and Tetragraptus. 

 The promontory of St. David's is now known to con- 

 tain them, especially at Llanvirn and Whitesand Bay 

 Abereiddy Bay is a good locality for finding Didymo- 

 graptus and Dicellograptus. At Tarannon, in North 

 Wales (a lovely neighbourhood to select for a walking- 

 tour), no fewer than twenty-three species of Graptolites 

 have been met with, distributed through five genera. 



The Skiddaw and Keswick district is usually rather 

 poor in fossils, although to the geologist this is atoned 

 for by the physical geology being among the most 

 interesting examples in Great Britain ; whilst for 

 beauty and diversity of scenery, it would be difficult 

 to find its equal in our land. In the black slates, the 

 geological student should look closely for Graptolites. 

 No fewer than twenty-seven species have been obtained 

 thereabouts. At Coniston, in the easily recognized 

 " mud-stones," we find another colony of Graptolites, 

 of which twenty-five species have been described. 



The Ludlow shales, in the Upper Silurian rocks, 

 saw the last of this ancient and easily identified group 

 of fossils. Only one genus of the Rhabdophora 



