CLASS I. ECHINODERMATA: ORDER 3. STELLERIDA. 627 



SAND-STAR. 



Gorgoti's Head^ witli 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 arc all 

 rare. The Shetland Argus, Astrophyton scutatur/i, usually more than a foot across, is sometimes 

 found on the British coasts. 



THE OPHIURID^ 



The Ophmridce, so called from the resemblance of their arms to serpents' tails, formino' the 



second family, derive their name from 

 the Greek ophis, a snake, and ou7-a^ 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 foand in the British 

 seas is the Common Brittle-Star, 

 Ophiocoma ros«7fl, Avhich displays the 

 most varied Imes, 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, Ophlura tcxitirata, 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 fnrrows, which run along 

 the lower surface of the arms. In 

 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 family 

 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-FINGERED JACK. 



