138 



ECHINODEllMATA. 



Fig. 58. 



and known in the northern districts of our own island, where they 

 are very abundant, as " St. Cuthberfs beads" 



Of the internal structure of the Encrinites nothing is satisfac- 

 torily known. That 

 they possessed a dis- 

 tinct 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.* 



(181.) Asteridce. 

 In order to convert an 

 Encrinus into an ani- 

 mal capable oflocomo- 

 tion, and'able to*crawl 

 about at the bottom 

 of the sea, little fur- 

 ther would be requi- 

 site than to separate 



the body and arms from the fixed pedicle upon which they are sup- 

 ported, and we should have an animal resembling in every particular 

 the star-fishes. The Comatula, for example, (fig. 58,) one of the 

 lowest of the asteroid Echinodermata, might be looked upon as an 

 animal thus detached. The central part, or body, which contains 

 the viscera, is made up of numerous calcareous pieces, having in 

 its centre a stelliform mouth, and near this is a tubular orifice which 

 might be regarded as an anus. Around the margin of the central 

 disc arise five stunted arms which immediately divide into a variable 

 number of long radiating branches, composed, like those of the En- 

 crinus, of innumerable articulated earthy masses enveloped in a liv- 

 ing and irritable integument. We find, moreover, issuing from 

 the sides of every one of the prolonged rays, a double row of se- 

 condary filaments, each containing an internal jointed skeleton, and 

 capable of independent motion. The complicated arms of the Co- 

 matula, therefore, are not, like those of a polyp, merely adapted 

 to seize prey ; but, from their superior firmness, may be used as 

 so many legs, enabling the animal to travel from place to place. 



* 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. 



