THE STONE LILIES OR CRINOIDS 



3267 



British seas this process has gone yet further; the animal breaks away from its 



stem when quite young, but retains the uppermost swollen and coalesced segments 



of the stem, which form one solid mass bearing a number of cirri, while the two 



lower circlets of cup plates almost entirely disappear, so that only the upper circlet 



of plates, from which the arms arise, remains. The Antedonidcs, which have all 



arisen since Jurassic 



times, include not only 



numerous species of An- 



tedon, but at least as 



many more of a closely 



allied genus, Actinome- 



tra, as well as three other 



less common genera, 



named Atelecrinus, Eudi- 



ocrinus, and Promacho- 



crinus. They are far 



more numerous at the 



present day than the 



stalked crinoids, and 



occur in all parts of the 



world, but their head 



quarters are in the East 



ern Archipelago. 



There are a few 

 crinoids that have 

 diminished their stem, 

 but have nevertheless 

 remained attached, so 

 that at last the cup has | 

 come to be fixed on the 

 sea floor without the 

 intervention of a stem. 

 Such a form is the 

 stumpy and thick-set 

 Holopus, which is among 

 the greatest rarities in 

 museums. It lives at 

 depths of about a 

 hundred fathoms in the 

 Caribbean Sea. Similar 

 forms occur in some of == 

 the shallow-water and | 

 reef deposits of Jurassic j|j 



and Cretaceous ages. ROSY FEATHER STAR, CLINGING TO A TUBE OK SABELLA WORM. 

 Many of these have (Natural size.) 



