152 RAMBLES AND REVERIES. 



a species of which we have chosen as an illustration 

 (Fig. 34). L. basaltiforme is a common rugose 

 compound coral. The lighter portion of the figure 

 shows the transverse structure as it appears in 

 microscopical sections. When mountain limestone 

 is weathered, it often looks as though covered with 

 dead twigs. The twig-like prominences are in 

 reality dense masses of corallites, and will very 

 likely turn out to be species of Lithostrotion. 



The genus Zaphrentis is another very common 

 Carboniferous coral, and may be found in a perfect 

 condition weathered out into relief on the limestone 

 walls. Lonsdalia looks out from the roadside in 

 many places in Derbyshire, North Wales, and Scot- 

 land. It would be impossible and confusing to 

 enumerate even the genera of Carboniferous corals. 

 They occur all through the four thousand feet of the 

 English Mountain limestone, which was probably 

 deposited on the floor of a slowly subsiding sea, and 

 are found in bewildering profusion in the lower 

 Carboniferous strata of Scotland, which seem to have 

 been laid in shallow waters. Besides those already 

 mentioned, it will be easy to obtain Aspidophyllum, 

 R/iodophyllum, Clisiophyllum, from Scotland and 

 elsewhere ; Gyathaxinia from the Lake district ; the 

 pretty Phillipsastrtea from Corwen ; and indeed 

 many kinds from every part of Britain where the 

 Carboniferous limestone occurs. 



The Permian formation follows the Carboniferous 

 system in geological succession ; and as is the case 

 with all other forms of animal life, so with regard to 

 corals, there is an almost complete extinction. So 



