54 " PROCEEDINGS OF THE 



Minute teeth project from the margin of each of these holes, and 

 appear to rise above the plane of the plate. Four teeth may be 

 observed on one side of a hole and three on the other ; at other 

 times, and perhaps as often, there are five on one side and four 

 on the other, nine in all; and, on some of the smaller ones, there 

 are only five altogether. Occasionally, but rarely, two or three of 

 these minute teeth or processes may be seen on the external 

 margin of one of the sides of the plate, and similarly one of these 

 may be incomplete, leaving a little opening into one of the holes, 

 the calcareous matter terminating in two points, as if its develop- 

 ment had been arrested before these points coalesced to complete 

 the circle around the hole. Other malformations occasionally 

 occur in the forms of the plate. 



Upon this anchor-plate the anchor lies, folded down, as it were, 

 at an acute angle, and projecting at the fluke end. The flukes 

 are sharp-pointed, and are frequently serrated on the outer margin. 

 In one example there was an open foramen at the fluke end of the 

 shaft, so that the anchor had somewhat the appearance of a double- 

 edged battle-axe. Near the other extremity the shaft bulges a 

 little, and again contracts next the cross-piece. The breadth of 

 the shaft is about the same as that of the process of the anchor- 

 plate. 



According to Mr Herapath (On the Pedicellarise of the Echino- 

 dermata. Quart. Jour. Microscop. Soc, Vol. v.), "These perforated 

 plates are the analogues of the pentagonal plates of an Echinus 

 shell, while the anchors are merely modifications of the spines, 

 and are used as organs for prehension and locomotion, and assist 

 the animal in raising its vermiform body to the mouth of its tube, 

 the anchors being withdrawn during the period of contraction of 

 the Syncqjta, and contribute little or nothing to the powers of 

 defending the animal from the attacks of its predatory enemies." 

 I cannot say whether such is the case or not; it appeared to me 

 that the anchor-flukes were sometimes covered by a thin 

 membrane. 



There is a very regular row of these anchors down each side of 

 the longitudinal muscles, and they are placed at right angles to 

 the muscle, the hinge-joint of attachment being nearest it, and 

 the round end of the plate, with the fluke end of the anchor, 

 pointing towards the space between the muscles. It is also that 

 part which projects when the muscle is contracted. The animal 



