2 20 THE BUILDING OF THE DERBYSHIRE LIMESTONE. 



the crown is preserved the resemblance is more complete. 

 Prolonged weathering shows these stems to be made up of a number 

 of joints having a thickness of a sixteenth of an inch or more. 



As our knowledge of the fatma and flora of the depths of the 

 sea was enlarged by the discoveries made during the Challenger 

 and other expeditions, the nature of the fossil contents of this 

 limestone became more and more clear. Forms of life bearing a 

 close resemblance to those described as occurring in a fossil 

 condition in the limestone were dredged up. That they lived in 





colonies was evident from the fact that when brought up there 

 were usually a number, and the mode of life of the extinct forms 

 may be inferred from those which are now living. They are termed 

 Crinoids, and certain genera existing at the present time are also 

 found fossil, as, for example, the form Pentacrinus. Fig. 3 is a 

 drawing of Pentacrinus wyville-thomsoni, which was dredged up 

 from a depth of 1,095 fatboms in the Mediterranean during the 

 voyage of the Porcupine. Only a portion of the stem is shown. 



