MUSEUM OF COMPARATIVE ZOOLOGY. 129 



The following description is not as full as could be wished, as the speci- 

 mens are not numerous or perfect enough to warrant a complete di-section. 



The calicle is in the shape of a regular elongated inverted cone. It is 

 composed of a cycle of elongated basal (pelvic) pieces, followed by the 

 much shorter first radials (costals) alternating with them. These pieces 

 are all so intimately connected with each other that the sutures are seen 

 with difficulty. The surface is perfectly smooth. The lirst brachials 

 are flat and square, and connected laterally by a membrane. The arms 

 generally break oil' between these and the second brachials, and the first 

 might therefore be called second radials, as they in a measure contribute 

 to the formation of the calicle ; still, as they are movable on the lirst radials, 

 and similar in shape to the next two joints, it is more natural to name 

 them as we have done. The next two joints, or second and third brachials, 

 are similar, and but little smaller than the first. The arms contract suddenly 

 at the fourth brachial ; they are five in number, simple, and composed of 

 forty joints, every pair of which forms a syzygium. The pinnules arise 

 from the side of the upper joint of each syzygium, alternately on one side 

 and on the other. There are none, however, on the four or five first 

 syzygia. The inner side of the arm is channelled, and the middle of the 

 channel is protected by a row of very thin alternate scales. 



The pinnules are composed of from ten to fourteen somewhat imbricated 

 plates, of which the first two are narrower than the subsequent ones. The 

 inner side is provided with a row of rounded alternate scales similar to 

 those on the inside of the arms. 



The stem is composed of a variable number of joints ; our largest speci- 

 men having fifty-nine and the smallest but thirty. The generic character of 

 having the joints flattened at their two ends in planes alternately at right 

 angles to each other is well marked, particularly near the root ; it is less 

 apparent near the calicle, though this conformation may still be recognized 

 to within half a dozen articulations of it; the last joints are sensibly round. 

 The length of a joint is on the average about three times its diameter, except 

 the four or five joints preceding the calicle, which are much shorter. The 

 joints are connected by a ligament passing through the central canal, also 

 by two strong ligaments lodged in parallel oval cavities in the articulating 

 surfaces, and finally by a membrane along the edge. This threefold con- 

 nection is so strong that by applying force it is more easy to break through 

 the body of the joint than to disconnect the articulation. 



The root is variable ; sometimes all its ramifications start from a single 

 joint, whilst in other specimens some five or six joints send out roots 

 from their upper compressed edges. Each root promptly subdivides into a 

 large number of rootlets ; the whole is formed of articulated joints, which 

 become much elongated as they become thinner. 

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