The Era of In ri ii>/> ni I* x 



most important agents in the formation of the 

 great beds of limestone in which their fossil re- 

 mains are preserved. There are few species of 

 crinoids now living, and these are mostly con- 

 fined to limited areas of veiy deep water and to 

 be obtained only by means of special appliances 

 for dredging in the deep 

 sea. So for a long time 

 even the most common of 

 them (Penta&nnus caput- 

 was very rare and 



regarded as one of the 

 great treasures of such mu- 

 seums as chanced to pos- 

 sess a specimen. The re- 

 searches of the United 

 States Fish Commission A modern crinoid /Vw , (| _ 

 steamer Albatross, how- crinu * caput - medium. 



. Much reduced. 



ever, brought to light a 

 locality in the Gulf of Mexico whence many 

 examples of this beautiful radiate have been 

 obtained, and other species have been discov- 

 ered by the Albatross and by the English 

 Challenger. Still, the group of crinoids is but 



79 



