﻿CARBONIFEROUS PERIOD 53 



tributed, and apparently did not greatly redound to the 

 welfare of their possessors (Hexactinellids) ; for sponges with 

 needles so elaborately developed had no representatives in 

 any later Period. 



1 Honey-comb ' corals of the kind that built up Silurian CORALS 

 and Devonian reefs were now declining (Favosites), but some 

 closely allied forms {Michelinia) were in great force in some 

 regions — notably in a sea that then extended over Belgium. 

 New colonies were also appearing with zooids enclosed in 

 porous body-walls ; and by means of connecting-tubes a 

 greater community of life was established than what had 

 hitherto obtained (Palceacis). These more communicative 

 corals were possibly ancestral forms of one of the great reef- 

 building families of the present time (Poritidce). 



Cystids, long on the wane, were now on the verge of cystids 

 extinction. 



Although abundant and diversified in some North American sea-lilies 

 waters crinoids appear on the whole to have been still 

 declining. The sanitary reformers, it is true, continued well re- 

 presented (Actinocrinus, Platycrinus, Batocrinus); but the elon- 

 gated waste-tube was by no means becoming general. Many 

 crinoids, without any notable safeguard against food-pollution, 

 continued fairly prosperous ; and some of these exhibited 

 remarkable robustness in the ventral region (Hydreionocrinus). 



A large number of crinoids were now in evidence with 

 clinging tentacles developed on the stem ( Woodocrinus). 

 Probably the stem-roots were wasting away, and the out- 

 growths arose as helps to meet initial difficulties attending 

 emancipation. A few forms indeed — at least in the adult 

 state — seem to have gained a complete freedom to move 

 from place to place (Agassizocrinus). This was an advance 

 to modernism : for locomotion is enjoyed by the majority 

 of crinoids now living. The family, whose members had the 

 mouth exposed in the manner in vogue at the present time, 

 had increased in genera ; but as regards numbers and distribu- 

 tion it continued insignificant (Ichthyocrinidcz). 



Fossils occasionally contribute to decorative art : and 

 Carboniferous crinoids, like Devonian corals, have been 

 immortalised in beautifully patterned marble. 



