chap. ix. J THE DEEP-SEA FAUNA. 437 



flattened calcareous joints ; it may be snapped over 

 at the point of junction between any two of these 

 joints, and by slipping* the point of a pen-knife into 

 the next suture a single joint may be removed entire. 

 The joint has a hole in the centre, through which 

 one might pass a fine needle. This hole forms part 

 of a canal filled during life with a gelatinous nutri- 

 ent matter which runs through the whole length 

 of the stem, branches in a complicated way through 

 the plates of the cup, and finally passes through 

 the axis of each of the joints of the arms, and of 

 the ultimate pinnules which fringe them. On the 

 upper and lower surfaces of the stem-joint there 

 is a very graceful and characteristic figure of five 

 radiating oval leaf-like spaces, each space surrounded 

 by a border of minute alternate ridges and grooves. 

 The ridges of the upper surface of a joint fit into 

 the grooves of the lower surface of the joint above 

 it ; so that, though from being made up of man 

 joints the stem admits of a certain amount of 

 motion, that motion is very limited. 



As the border of each star-like figure exactly 

 fits the border of the star above and below, the five 

 leaflets within the border are likewise placed directly 

 one above the other. "Within tbese leaflets the 

 limy matter which makes up the great bulk of the 

 joint is more loosely arranged than it is outside, and 

 five oval bands of strong fibres pass in the inter- 

 spaces right through the joints, from joint to joint, 

 from one end of the stem to the other. These 

 fibrous bands give the column great strength. It 

 is by no means easily broken even when dead and 

 dry. They also, by their elasticity, admit a certain 



