CHARACTERISTIC DEEP-SEA TYPES. OPHIURANS. 113 



wash increases the already abundant supply of lime, a substance 

 that forms nearly the entire weight of some species ( Ophiomas- 



Fig. 397. Ophiomyces frutectosus. 



tus secundus, Fig. 398). These conditions naturally give rise 

 to much variety in form, and to a great abundance of individu- 



als. The nine species mentioned by Miiller and Troschel, in 

 1842, as belonging to this area, have increased to one hundred 

 and fifty-five, which are distributed at various depths. On the 

 flats and reefs, near islands and keys, may be found colonies of 

 Ophiothrix, blue, green, or red, with their translucent thorny arm- 

 spines, and the humble Ophiactis swarming on great sponges ; 

 while here and there a yellow or vermilion star marks the soft 

 Ophiomyxa flaccida. To the brown gorgonians clings the large 

 Ophiocoma, similar in color ; and sometimes a Medusa-head, 

 whose branching arms excited the wonder of old Rondelet, 

 twines about the thicker stems. These and their companions, 

 living in a strong light, and in warm shallow water, present 

 brilliant and well-marked colors. Nor are those that inhabit the 

 dark and cold depths of the ocean always pale ; on the contrary, 

 many are of a bright orange or red. They are peculiar, how- 

 ever, in that their colors generally fade in alcohol ; and in an 

 alcoholic collection the shallow species may readily be distin- 

 guished by their brighter coloration. 



