122 OUR COMMON BRITISH FOSSILS. 



may be found thus dispersed over the surfaces of the 

 Carboniferous limestone whose fragments are used for 

 wall-building. In Clitheroe, Lancashire, at a small 

 elevation known as Salt Hill, the rock is built up 

 of Encrinite stems. In this 

 case, however, the fossils are 

 loose and incoherent, stems 

 and ossicles lying together 

 almost uncemented by any 

 matrix, or by one which 

 speedily weathers and liberates 

 the fossils. The consequence 

 is that joints and short stems 

 of Encrinites are so loose and 



,,. abundant that they are pro- 



Fig. 104. Head of Poteriocrinus. J 



cured as a kind of limy gravel 

 to mend or make garden paths with ! 



Some of these abundant Encrinite stems in Derby- 

 shire are often more than one inch in diameter. One 

 species, known as Poteriocrinus crassus, was the most 

 widespread and abundant of all the Carboniferous 

 Crinoids. The head, or body of the Encrinite, was 

 tapering, and in this respect it resembled the singular 

 little Rhizocrinus lofotensis brought up from the 

 bottom of the North Sea, in the living state, by 

 Messrs. Carpenter and Wyville Thomson during one 

 of their earlier dredging expeditions. This Rhizo- 

 crinus is one of the last survivors of a once cosmo- 

 politan race of animals, now all but extinct, whose 



