120 OUR COMMON BRITISH FOSSILS. 



material, such as was deposited between the joints, so 

 arranged around the filled-up hollow of the so-called 

 " alimentary " canal down the whole length of the 

 stem, as to give it the appearance of the screwed end 

 of a bolt. For mile after mile the geologist walks 

 along the Derbyshire mountain roads and finds the 

 stone walls on either hand composed of little else than 

 encrinital remains. Sometimes the rock containing 

 them is very hard, and then it will be worked as 

 marble; which, when polished, is used for mantel- 

 pieces. Many of my readers must be acquainted 



Fig. TOO. Head of Fig. 101. Lower part of stem 



Rhodocrinus (Car- of Encrinite, showing mode 



boniferous limestone). of attachment to sea-bottom. Fig. 102. Cupressocrintts. 



with this polished grey marble, full of all sorts of 

 objects, but especially of these Encrinite stems, cut 

 across, lengthwise, or at all kinds of angles, so that 

 the appearance varies with each individual fossil. 

 When the limy matrix is quite black (as it is at 

 Ashford, near Bakewell), the marble is all the more 

 valuable for economic purposes, for the white fossils 

 then stand out in splendid distinctness from the jet- 

 black stone in which they are imbedded. The stones 

 of the mountain roads are usually picked off the 



