OPHIUR1D&. 



271 



This disc is from six-eighths to seven-eighths of an inch in size, the 

 upper part covered with unequal plates, in shape like tiles ; the arms 

 are four times the length of the diameter of the' disc, very slender and 

 tapering. The Ophiuroid to which Lamarck gave the name of 



Fig. 109. Ophiocoma Riisei (Lutken), natural size. 



Ophiurafragilis has now its place in the genus Ophiothrix, the specific 

 name indicating a peculiarity of structure in all these small creatures 

 derived from their fragile formation. In short, these beings have so 

 little consistency, that many of them crumble as it were under the 

 touch, and become reduced to pulp under the slightest pressure. 

 In Fig. 109 we give the representation of an Ophiuroid of the natural 



