68 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [362] 
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. 266,) 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 fragmeats. 
Another related species, LZ. 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 muéh 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 skinis 
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 isfilled with immense numbers of small, round, 
wheel-like plates, with an uneven or undulated border, perforated near 
the rim with ten to twelve roundish openiogs, 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 patts. 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 papille, 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,” Echinarachnius parma, (Plate XXXV, 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 sbore, except at 
extreme low water of spring-tides, when it may sometimes be found 
on flats or bars of fine siliceous sand in great numbers, buried just 
beneath the surface, or even partially exposed. Itcreeps 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 saudy bottoms at various depths off shore. Ithas a very wide range, 
for it is found all the way from New Jersey to Labrador, and also on 
