124 ANNULOIDA. 



The dorsal surface of the cup or " calyx" is composed of a 

 number of calcareous plates accurately fitted together. The 

 number and arrangement of these vary much in different 



Fig. 78. 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-arms. 



genera, and it will be sufficient to indicate here their general 

 disposition. Reposing directly upon the summit of the column 



