FOSSIL SPONGES, ETC. 17 



Apart from fossilizing for Stromatopora certain to 

 be found in most quarries where the Upper Silurian 

 or Devonian limestone is worked until we come 

 to the Carboniferous limestone we should hardly 

 reckon our sponge "finds." Calcispongia, Protospongia, 

 Ischadites, Astylospongia> and Amphispongia are not 

 uncommon Silurian genera found near the Malverns, 

 at Ludlow, and in the Longmynds. Fifteen species 

 of sponges are described from the Carboniferous 

 limestone, Palceacis being the commonest. The young 

 hunter for this kind of geological spoil should first 

 make himself acquainted with the various appearances 

 of sponge structure under the microscope with the 

 fibrous as well as the spicular details. Then he will 

 be prepared, when out on his rambles, to examine 

 any suggestive materials. One of the most profitable 

 geological rambles, in this respect, I ever experienced 

 was on the Carboniferous limestone of Black Head 

 in County Clare a spot not likely to be soon for- 

 gotten by those who love natural scenery. The 

 limestone is traversed by numerous joint-fissures, in 

 which grow the loveliest of ferns, the maidenhair 

 (Adiantum capillus-veneris] being especially luxuriant 

 and abundant. Before us break the rollers of the 

 wide Atlantic ; behind us the hills rise in gentle 

 slopes for they are formed of black, fossiliferous 

 Yoredale shales. 



The walls by the roadside, which take the place 

 of hawthorn hedges, are crowded with fossils. Some 



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