646 THE WONDERS OF GEOLOGY. Lect. VI. 



lated together in regular series along the margins of the 

 rays, which are therefore strong and flexible. A longitu- 

 dinal furrow extends from the mouth to the extremity of 

 each ray, the sides of which are perforated by alternating 

 rows of pores, for the exsertion of tubular tentacula. 



Some kinds of Star-fish (the Co-mat ulce, or Feather Stars), 

 instead of the five flat rays, have jointed arms, that pro- 

 ceed from a central cup-shaped calcareous base, and divide, 

 and subdivide into delicate jointed tentacula, the sides of 

 which are fringed with rows of still smaller articulated 

 pinnse, or processes.* Now, if we imagine a Comatula 

 placed with its mouth upwards, and fixed on the top of a 

 jointed stem by the centre of its dorsal surface, we have the 

 essential type of the Crinoideans, or Lily-shaped animals, 

 so named from a fancied resemblance of some of the species 

 when in a state of repose to a closed lily. The only known 

 living genus of this family inhabits the seas around the 

 West Indies ; and of this sole representative of the nume- 

 rous crinoideans of the palaeozoic ages, but five or six speci- 

 mens have been brought to Europe. It belongs to that 

 subdivision in which the joints of the column are penta- 

 gonal, and is therefore named Pentacrinus. 



38. Structure of the Crinoidea. — From this recent 

 example {JLign. 144), which does not essentially differ from 

 the extinct forms, an accurate knowledge of the structure 

 of these curious animals has been obtained. The Cri- 

 noideans are characterized by having a root or process of 

 attachment, by which they are fixed at the base to the rock ; 

 a stem composed of numerous articulations, or separate 

 pieces of a solid calcareous substance ; and a cup or vase 

 at the summit of the stem, which contains the body or 

 viscera of the animal, and from the upper border of which 



* The living British Star-fishes are beautifully figured in Pro! 

 E. Forties's charming work, published by Van Voorst, 1841. 



