CLASS I. ECHINODERMATA: ORDER 3. STELLERIDA. 627 
SAND-STAR. 
Gorgon^ s Head, with, its snaky locks. These animals, which swim with outspread arms, and capture 
their prey by involving it in their numerous branched rays, are principally found in the tropical 
seas, although some species exist even in the icy waters of the Arctic regions. They are all 
rare. The Shetland Argus, Astrophyton scutatum, usually more than a foot across, is sometuues 
found on the British coasts. 
THE OPHIURIDJS. 
The Opkiuridce, so caUed from the resemblance of their arms to serpents' tails, forming the 
second family, derive their name from 
the Greek ophis, a snake, and oura, a 
tail. The body consists of a roundish 
disc, furnished with five or more long 
simple arms, edged with movable 
spines, which have no furrow for the 
protrusion of the ambulacra. They 
pass under the popular names of 
Brittle Stars and Sand-Stars. They 
are exceedingly plentiful in most 
seas, and their fossil remains occur in 
all the more recent marine strata of 
the earth's crust. Among the sev- 
eral species found in the British 
seas is the Common Brittle-Star, 
Ophiocoma rosula, which displays the 
most varied hues, arranged in beau- 
tiful patterns. Like the other Brit- 
tle-Stars, it breaks in pieces when 
alarmed or irritated ; " touch it, 
and it flings away an arm ; hold it, and in a moment not an arm remains attached to the body." 
Among the British species are the Common Sand-Star, Ophmra texturaia, and the Lesser 
Sand-Star, 0. albida, which have also 
the brittleness of the species just de- 
scribed. 
THE ASTERID^. 
We now come to the Asteridce, of 
which the Star-Fish, popularly called 
Five-fingered Jack, so abundant on our 
coasts, is an example. In this family 
the arms appear to be merely pro- 
longations of the disc ; they are usually 
five in number, and the plates from 
which the ambulacra are exserted are 
placed in deep furrows, which run along 
the lower surface of the arms. Li 
some species the arms are very short, 
and in others the animal forms a flat 
pentagonal disc, with five ambulacral 
furrows excavated in its lower surface. 
In the center of this the mouth is sit- 
uated, and the ramifications of the 
stomach extend to a greater or less distance into the arms. Most of the species of this famil}^ 
possess an anal aperture ; but this is wanting in some. These animals feed on worms and various 
kinds of shell-fish, sometimes clasping and sucking out the flesh of the latter ; they often accom- 
FIVE-FINGfEEED JACK. 
