CRINOIDEA 15 



known to feed regularly on Crinoids. The regenerating power of 

 sea-lilies is exceedingly great. On being hurt, or on being kept 

 under unfavourable conditions, they throw off not only the arms 

 but often also the whole disk, with mouth, intestinal canal, etc., 

 and easily regenerate it all again. 



On the sea-lilies there is almost constantly found a remarkable 

 parasitic animal, Myzostoma (Fig. 5), a sort of peculiarly trans- 

 formed Chaetopod, with a rather long, protrusile proboscis. 

 Generally it creeps freely along on the disk and arms, moving 

 rather swiftly ; some species form a sort of gall or cyst, 

 in which thej^ live. 



Sea -lilies were much more numerously represented in former 

 geological epochs than they are in recent time, excepting only 

 the Comatulids. Fossil remains of sea-lilies 

 are therefore exceedingly numerous, and are 

 of the highest importance, both from a geo- 

 logical and a zoological point of view. While 

 the stalked Crinoids are very often found in 

 a perfect state of preservation, usually only 

 the centro-dorsal and more rarely a few 

 of the first brachials are found of fossil 

 Comatulids. ^ 



Four families of Crinoids are represented 'cirrijerwn " Leuc- 



in British seas ; possibly, however, four l^art, parasite of 



more will ultimately prove to occur in the withprob^^^^^^^^ 



deep sea off Ireland, viz. the family I so- truded. x 7. (After 



crinidcB, one genus and species of which, Lo ven ; from i)aM- 



, ^ ^ . 7nark s Fauna.) 



Annacrinus Wyville- Thomsoni (Jeffreys), 



(s}Ti. Pentacrinus Wyville- Thomsoni Jeffreys), is known from 



the Ba}^ of Biscay, southward to the Canaries, ca. 1330-2000 m. 



("Porcupine ", " Talisman ", " Princesse Alice ") ; the family Hyo- 



criniclce,^ with the one genus and species Gephyrocrinus Grimaldii 



Koehler and Bather, known from off Madeira and the Canary 



Islands to the equatorial mid- Atlantic, 1786-3382 m. ("' Princesse 



Alice ') ; the family Thalassometridce, three genera of which are 



represented in the N.-E. Atlantic (cf . below, p. 25), and the family 



Comasteridce, one genus and species of which, Neocomatella 



europcea A. H. Clark, has been found from off Brittany (48° 07' N.) 



to S. of the Canary Islands, 400-1710 m. ('"' Porcupine "). These 



four families are included in the following key : 



^ A. H. Clark ('* Ingolf " Crinoidea) regards Gephyrocrinus and some 

 other recent Crinoids (Hyocriniis, Ptilocrinus) not known from the Atlantic 

 as belonging to the family Plicatocrinidoe. 



