62 NATURAL HISTORY OF OUR SHORES 



deeper water, is the " Common Brittle Star " (Ophiothrix 

 jragilis). This is a very popular form, and is the one 

 usually figured in elementary books of zoology. Its disc 

 is about half-an-inch across, and its rays spread to a compass 

 of about five inches. The rays are beautifully set with 

 radiating spines. Its colour is usually red and white ; 

 or red and yellow, the colours arranged in alternate bands 

 across the rays. 



A larger species, closely similar in form, is sometimes 

 met with. This is Ophiothrix niger. Its colour is nearly 

 black, and the radiating spines of the rays are buff. In the 

 Channel Islands it is common on coralline, or rather Nullipore 

 bottom, in ten to fifteen fathoms of water, and is taken in 

 the dredge. 



The common " Cross -fish " (Uraster rubens), usually 

 taken as the type of the whole class, is frequently cast on 

 shore from deep water, but also lives regularly on shelly 

 gravel bottom and among loose stones. It is about six or 

 seven inches across its rays or " arms." These, unlike the 

 corresponding parts of those we have mentioned, are stout, 

 and form the greater part of the animal's bulk, no definite 

 " disc " being apparent. Its colour is buff, drab, or slaty 

 grey. 



The Great Spiny Star-fish (Uraster glacialis) bears some 

 resemblance to the last, but is much larger, sometimes 

 twenty to twenty-four inches across its arms. It is strongly 

 armed with stiff spines, the bases of which are surrounded 

 with velvet-like tufts of very fine ones. Its colour is 

 something between a purple and a greyish buff (Fig. 23). 



It is found in rocky situations, sometimes squeezed in 

 very unstarlike form in rock crannies. It is frequently 

 taken by fishermen on their lines, having engulfed the bait 

 intended for more marketableTdenizens of the sea. This 

 species, and the previous one, often cause great havoc in 

 oyster-beds, destroying large numbers of the molluscs. 



