10 STRUCTURE OF THE CYSTIDEJE. 



seen rel}^ to one spot on 'the bottom of the ocean throughout life; 

 and at the opposite, or upper end, a set of arms, which, in addition 

 to their other functions, may have assisted in the collection of food 

 by exciting currents of water towards the mouth. This latter 

 organ was a circular or oval aperture, situated in the side, below 

 or near the summit, and in some species must have been also the 

 passage through which such matter as could not be digested was 

 thrown out. The young were developed from eggs, which were, 

 there is good reason to believe, generated in the grooves of the 

 arms or pinnulae, where, as has been ascertained by actual observa- 

 tion, the organs of reproduction are situated in the Crinoids that 

 exist in some of the seas of the present time. 



Concerning the food, habits, or other particulars of the natural 

 history of the Cystideae, we can never hope to acquire any great 

 amount of information, as the race wholly perished many ages ago, 

 and the only evidences we have of its existence are, with few 

 exceptions, very imperfect skeletons, which exhibit nothing except 

 the structure of the external hard parts. It is only probable that 

 their nourishment was derived from minute particles of animal or 

 vegetable matter diffased through the waters in which they lived. 

 The structure and position of the mouth are such, that they could 

 not have been highly carnivorous, while their nearly sedentary 

 condition would altogether preclude the capture of any prey except 

 such as might float by chance within their reach. Animals rooted 

 to the ground like a plant would fare ill were they organized to 

 support life by the predacious mode only. 



The fossil remains of the Cystideas consist for the greater part of 

 mere fragments of the plates and columns ; but these, in certain 

 localities, occur in such prodigious abundance, that they constitute 

 the principal portion of strata of rock several feet in thickness. 

 Of many of the species specimens of the bodies are exceedingly 

 rare, and when these are discovered they are usually more or less 

 crushed and distorted. While the fossil Corals, Brachiopods and 

 Gasteropods may be collected in hundreds, few cabinets can boast 

 of half-a-dozen good Cystideans, even in those countries where 

 whole formations of rock are composed of the exuvice of the race. 



With respect to their distribution in time, they have been dis- 

 covered in Bohemia, by M. Barrande, in beds which lie in the very 

 bottom of the oldest rocks containing traces of animal life ; and 

 therefore, according to the present state of our knowledge of the 

 primeval fauna, they were among the first living things that made 



