330 



THE INHABITANTS OF THE SEA. 



liily-Bnorinite. 



issues. When the animal wishes to protrude its feet, each 

 vesicle forcibly contracts, and, propelling the fluid into the cor- 

 responding sucker, causes its extension; and, when it desires 

 to withdraw them, a contraction of the suckers drives back the 

 fluid into the expanding vesicles. The internal walls of the 

 suckers and their vessels are furnished with vibratory cilia, and 

 by this simple means a continual circulation of the fluid they 

 contain goes on within them. 



Numerous species of star-fishes are so very common in our 

 waters, that in many places the sea-bottom is literally paved 

 with them. They likewise abounded in the primeval ocean, for 

 deep beds of carboniferous limestone and vast strata of the 

 triassic muschelkalk are often formed by the 

 accumulation of little else than the skele- 

 tons of Encrinites and Pentacrinites, which, 

 unlike the sea-stars which every storm drifts 

 upon our shores, did not move about freely, 

 but were affixed to a slender flexible stalk, 

 composed of numerous calcareous joints con- 

 nected together by a fleshy coat. The 

 feathered bifurcated arms of the Crinoids 

 are unprovided with suckers, which would have been perfectly 

 useless to creatures not destined to pursue their game to any 

 distance, but passively to receive the nutriment 

 which the current of sea-water set in motion 

 by their richly- ciliated pinnules conveys to the 

 mouth. These beautiful creatures were for- f 

 merly supposed to be nearly extinct, for up to 

 within the last few years only two living 

 stalked crinoids were known in the ocean of 

 the present period, but the dredge has latterly 

 brought up new and remarkably fine species 

 from depths of more than 2000 fathoms, and 

 there is every reason to believe that these 

 animals still form an important element in 

 the abyssal fauna.* 



Of freely-swimming Crinoids but one single representative is 

 known in the northern seas, the Kosy Feather-star (Comatula 

 rosacea), whose long and delicately fringed rays and deep rose 



* See page 420. 



Portion of the Pen- 

 taorinus Briareus. 



(Fossil.) 



