PENTACRINUS EUROP.EUS. 179 



they present the appearance of mere rings or plates ; 

 so that it is probably here that successive articulations 

 are formed, which add to the increasing length of the 

 stem as the animal advances in its growth. 



The exterior of the stem, as well as of the pieces 

 composing the body and rays, is invested by a con- 

 tinuous delicate membrane which binds them toge- 

 ther, and furnishes the requisite support to the mus- 

 cular system, which their motions lead us to suppose 

 they must necessarily possess, and which is probably 

 no other than what presents itself under the appear- 

 ance of a gelatinous translucent substance interposed 

 between this membrane and the ossicula. The animal 

 possesses the power of bending or inclining the stem 

 freely in every direction, and, what is more remark- 

 able, of twisting it up in a short spiral, and that with 

 a considerable degree of vivacity. 



The arms or rays surrounding the flower-like body 

 are five in number, but at the second joint each of 

 them divides into two, so as to represent a star with 

 ten rays. These branches or divisions of the arms 

 are each composed of a single series of solid calcareous 

 joints, about twenty-four in number, diminishing 

 gradually in thickness from their origin upwards ; at 

 either side they are fringed with soft tentacula, which 

 are jointed, and capable of considerable contraction 

 and extension. These tentacula, which are moved 

 in every direction, arise from the opposite sides of the 

 rays in an alternate order, and when highly magnified 

 appear to be themselves furnished with cilia, placed 

 alternately along their sides. It is these arms, com- 

 posed of numerous joints, and fringed with tentacula, 



