CRINOIDEA. 26*7 



greater detail. In the first place, as regards the " column," 

 we find that the stem of attachment is composed of a great 

 number of separate plates or " articulations " placed one 

 above the other, and so jointed to one another that whilst 



Fig. 157. Pentacrinus fasciculosus, showing the form of the column, and one of the facets 

 of a joint. The central figure shows the arms, and the summit of the column with side-amis. 



the amount of movement between any two pieces must be 

 very limited, the entire column acquires more or less flexi- 

 bility. In the Palaeozoic Crinoids, with few exceptions, the 



