CEINOID^l. ASTEKIDJL. 163 



to us the real structure of a race of animals once so common, but now 

 almost completely extinct. The body of the Encrinus (fig. 80, a) (or 

 pelvis, as the central portion of the animal is termed by geological 

 writers) is composed of numerous calcareous pieces, varying in shape 

 and arrangement, so as to become important guides to the identification 

 of fossil species ; from this central part arise the large rays (b 6), each 

 furnished with a double row of articulated appendages, which, as well as 

 the arms, are no doubt instruments for seizing prey and conveying it to 

 the mouth, situated in the centre of the body, near the point a. This 

 part of the animal, when found in a fossil state, from its resemblance to 

 a flower, has received the common name of a " lily-stone." 



(434.) The body above described, with the rays proceeding from it, is 

 supported upon a long pedicle (e), divided into countless segments ; and 

 upon the sides of the stem, similarly- constructed filamentary branches 

 are fixed (d cT) at equal intervals. The skeleton of an Encrinite consists, 

 therefore, of thousands of regularly-shaped masses of calcareous earth, 

 kept together by the living and irritable flesh in which they are im- 

 bedded ; and it is to the contractions of this living investment that the 

 movements of the animal are due ; but after the death of the creature, 

 and the consequent destruction of its soft parts, the pieces of the earthy 

 framework become separated and fall asunder, forming the fossil remains 

 called " Trochi" and known in the northern districts of our own island, 

 where they are very abundant, as " St. Cuthbertfs beads" 



(435.) Of the internal structure of the Encrinites nothing is satisfac- 

 torily known. That they possessed a distinct mouth and anal aperture 

 is evident from the structure of the plates of the body ; but this is the 

 extent of our information concerning them*. 



(436.) ASTEEID^:. In order to convert an Encrinus into an animal 

 capable of locomotion and able to crawl about at the bottom of the sea, 

 little further would be requisite than to separate the body and arms 

 from the fixed pedicle upon which they are supported ; we should then 

 have a creature resembling in every particular the Star-fishes. The 

 Comatula, for example (fig. 81), one of the lowest of the asteroid Echino- 

 dermata, might be looked upon as an animal thus detached. The 

 central part, or body, which contains the viscera, is made up of nume- 

 rous calcareous plates, having in its centre a stelliform mouth ; and near 

 this is a tubular orifice, probably to be regarded as an anus. Around 

 the margin of the central disk arise five stunted arms ; but these imme- 

 diately divide into a variable number of long radiating branches, com- 

 posed, like those of the Encrinus, of innumerable articulated earthy 

 pieces enveloped in a living and irritable integument. We find, more- 

 over, issuing from the sides of every one of the prolonged rays, a double 

 row of secondary filaments, each containing an internal jointed skeleton, 



* For a detailed account of the fossil Encrinites, the reader is referred to 'A Natural 

 History of the Crinoidea, or Lily-shaped Animals/ by J. S. Miller. 4to, Bristol, 1821. 



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