STARFISHES, SEA-URCHINS, ETC. 97 



The body is more or less cylindrical and looks not unlike a 

 cucumber, perhaps still more like a sausage. The body-wall 

 is tough and leathery and the five rows of tubular feet are 

 usually, but not always, present. At one end is a ring of 

 branched tentacles surrounding the mouth. These are often 

 flower-like or leaf-like and brightly colored. In the Orient 

 sea-cucumbers are largely used as food, the gathering and 

 preparing of this trepang, as it is called, forming a very con- 

 siderable industry. 



Many of the feather-stars or sea-lilies, class Crinoidea (Gr. 

 krinon, lily; eidos, likeness), are fixed to rocks or the sea bottom 

 by a longer or shorter stalk which is composed of a number of 

 segments. Others are attached by a stalk during their larval 

 stage, but after a time the stalk is absorbed and the feather star 

 becomes free. The central disk is provided with a number of 

 radiating arms which are long and slender, sometimes re- 

 peatedly branched. The fine lateral pinnulce on these arms 

 give them a feather-like appearance. They occur mostly 

 in deep water. There are comparatively few species of crinoids 

 that still exist, but in former geologic times thousands of 

 species flourished. The fossilized parts of their bodies, 

 especially the little disk-like segments of the stem, are very 

 common in Paleozoic rocks. 



