CRINOIDEA. COMATULA. 469 



are attached, during a portion or the whole of their lives, by a 

 peduncle, or footstalk, to some solid body. They all seem to 

 possess two orifices to the digestive cavity. Of this Order the 

 Cotnatula is the most abundant example ; and as its organisa- 

 tion is better understood than that of any other genus, our no- 

 tion of the character of the group is principally derived from 

 it. In general form, the Comatula does not depart widely from 

 some of the animals just described. The star4ike aspect is still 

 regularly preserved; and the mouth is in the centre of what 

 must yet be regarded as the under surface of the body. The 

 viscera are contained in the central disk, which is composed of 

 numerous polygonal plates. The arms arising from this disk 

 are five in number; but . they speedily subdivide, each usually 

 separating into four. These are composed of a number of calca- 

 reous pieces, solid and nearly cylindrical, which are inclosed in 

 a living flesh of greater thickness than the integuments of the 

 Asterice. Thus we have seen the rays, which in the Asteriae 

 contained the principal part of the animal, first deprived of the 

 prolongation of the stomach, and then losing their cavity alto- 

 gether, so as to become mere locomotive appendages to the 

 central disk. To the skeleton of the arms, we find that jointed 

 lateral appendages, of a similar structure, are attached ; and these 

 also are clothed with the fleshy integument which secretes them. 

 Between these lateral appendages is a slight furrow, occupied by 

 papillae, which are furnished with vibratile cilia ; and it appears 

 to be principally by the action of these cilia, that food is brought 

 towards the mouth. Although the digestive cavity has two 

 orifices, it is not constructed upon the plan of .that of the 

 Echinida. There is no separate alimentary canal ; but only a 

 stomach like that of the Asterice, with a short tubular prolonga- 

 tion, of which the orifice projects between the mouth "and the 

 side of the disk. (This projecting orifice, which is very evident 

 in the Encrinites, has been commonly mistaken for the mouth, 

 which is much less apparent.) At the surface of the disc opposite 

 to the mouth, the Comatula is furnished with a number of short, 

 jointed arms, which serve it in place of legs for adhering to 



