362 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



burrowing as well as for other purposes. The skin is filled with minute 

 perforated oval plates, to each of which there is attached, by the shank, 

 a beautiful little anchor, (fig. 268,) quite invisible to the naked eye. 

 The flukes of these anchors project from the skin and give it a rough 

 feeling when touched ; they afford the means of adhesion to various 

 foreign substances, having a rough surface, and are doubtless useful to 

 them when going up and down in the burrows. When kept in confine- 

 ment this species will generally soon commence to constrict its body, at 

 various points, by powerful muscular contractions, which often go so 

 far as to break the body in two, and after a few hours there will usually 

 be nothing left but a mass of fragments. 



Another related species, L. roseola V., also occurs in similar places 

 and has nearly the same habits, but this species is of a light rosy color, 

 caused by numerous minute round or oval specks of light red pigment 

 scattered through the skin. The anchors are similar but much more 

 slender, with the shank much longer in proportion. The perforated 

 plates are also much smaller in proportion to the length of the anchors. 



The Caudina arenata is much more rare in this region. It lives at 

 extreme low-water mark, or just below, buried in the sand. Its skin is 

 thicker and firmer than that of the preceding species, and its body is 

 shorter and stouter, while the posterior part narrows to a long slender 

 caudal portion. Its skin is filled with immense numbers of small, round, 

 wheel-like plates, with an uneven or undulated border, perforated near 

 the rim with ten to twelve roundish openings, and usually having 

 four quadrant-shaped openings in the middle ; or they may be regarded 

 as having a large round opening in the middle, divided by cross-bars 

 into four parts. This species appears to be rare in this region, and was 

 met with only by Professor H. E. Webster, at Wood's Hole, but it is 

 quite abundant in some parts of Massachusetts Bay, as at Chelsea 

 Beach and some of the islands in Boston Harbor. These and all other 

 holothurians are devoured by fishes. 



The Thyone Briareus is a large purple species, often four or five inches 

 long and one inch or more in diameter. It is thickly covered over its 

 whole surface with prominent papillae, by which it may easily be distin- 

 guished from any other found in this region. It is more common in 

 the shallow waters off shore, on shelly bottoms. 



The " sand-dollar," Eeliinaraclinius parma, (Plate XXXY, fig. 267,) 

 is the only sea-urchin that is commonly met with on sandy shores in 

 this region, and this is not often found living on the shore, except at 

 extreme low water of spring-tides, when it may sometimes be found 

 on fiats or bars of fine siliceous sand in great numbers, buried just 

 beneath the surface, or even partially exposed. It creeps along beneath 

 the sand with a slow gliding motion, by means of the myriads of minute 

 extensile suckers with which it is furnished. It is far more abundant 

 on sandy bottoms at various depths off shore. It has a very wide range, 

 for it is found all the way from Xew Jersey to Labrador, and also on 



