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MANUAL OF ZOOLOGY. 



continued over the ventral surface of the calyx, but stop short 

 at the bases of the arms. Hence they are continued as 

 covered passages or tunnels to a central point in the ventral 

 surface of the disc. Here, it is believed, is placed the mouth, 

 concealed by the calcareous plates of the perisome. 



Of the living stalked Crinoids, the best known is the Penta- 

 crinus Caput-Medusce, of the Caribbean Sea. More recently a 

 stalked Crinoid has been discovered in the Atlantic and North 

 Sea, and has been described under the name of Rhizocrinns 

 Lofotensis (fig. 62). The chief interest of this form is the fact 

 that it belongs to a group of the Crinoidea hitherto believed 

 to be exclusively confined to the Mesozoic Rocks viz., the 

 Apiocrinidce or " Pear-encrinites." In fact, Rhizocrinus is very 

 closely allied to the Cretaceous genus Bourgutticrinus, and it 

 may even be doubted if it is generically separable from it. 

 The late remarkable researches into the life of the deeper parts 

 of the ocean have brought to light several new Crinoids, which 

 will doubtless, when fully investigated, still further fill up the 

 interval between the living and extinct Crinoidea. 



Fig. 64. Crinoidea. Comatula rosacea, the Feather-star; a Free adult ; 

 b Fixed young. (After Forbes.) 



In the second type of the Crinoidea represented in our seas 

 by the 'Comatula (fig. 64), or Feather-star the animal is not 



