316 THE BRITISH NATURE BOOK 



The Sun Star (Solaster papposa) is recognized by its red colour, blotched with 

 white, and its twelve or fifteen rays. 



The Gibbous Starlet, or CUSHION STAR (Asterina gibbosa), is like a little 

 cushion, the space between the rays being filled up. 



The Bird's-foot Starfish (A. ornithopus) has its rays joined together by 

 a membrane, much like the toes of a duck's foot, and is thus immediately 

 recognized. 



The Feather Stars are beautiful animals, living in deep water. The Rosy 

 Feather Star (Comatula rosacea) has five rays, each forking into two, and 

 feathered with egg-holding appendages. It is tinted bright rose-red. 



The Brittle-stars have five active arms,. which, being jointed, move freely 

 in all directions. They readily snap off their arms when alarmed. They are 

 to be sought for under stones at low-water mark. 



One of them (Ophiocoma neglecta) is very minute, and although common 

 is seldom seen, on account of its size ; but it is a most interesting object in an 

 aquarium. 



The Eed Brittle-star (Ophiothrix rosula) is quite common, and one of the 

 handsomest and most variable in colour; but it is very seldom taken whole, 

 as it sheds its arms at the slightest touch. Parts of it are found often enough 

 among the debris in a fisherman's boat. 



The Sea Cucumber (Cucumaria pentactes) at first sight would not appear 

 to have any relationship with starfish or sea urchins, but it is in reality closely 

 allied. The body has no spines or plates, and is much more like that of a 

 slug ; but there are ten rays round the head, and the body has five distinct 

 angles, and there are other internal points of resemblance. 



It is greyish white in colour, and is found in dark rock pools. When alarmed 

 it throws off portions of its inside organs its teeth, throat lining, etc. becoming 

 almost a mere skin, but it speedily recovers and grows new organs. 



SEA URCHINS. 



These are very unlike starfish in outward appearance, but closer study 

 reveals their near relationship. The fact is that if you were to take a starfish 

 and double up its rays until the tips touch, and then petrify it, you would 

 have a sea urchin, for this latter has a limy shell consisting of five segments, 

 covered with spines in place of the starfish's bosses of lime, and with two 

 rows of small holes on each segment, through which the feet are protruded 

 when required. There is also the same hydraulic system of tubes and pipes 

 as in the starfish. At the meeting-place of the five segments are five " ocular 

 plates," each bearing an eye-spot. The spines of starfish are movable, and 

 when a section of one is seen under the microscope it presents a most exquisite 

 patterned appearance. 



There is a large mouth, and five teeth, with enamel-pointed tips the whole 

 forming an elaborate masticating structure still known as the " Lantern of 



