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HOLOTHURIADiE. 



the Psolidj;!, or Ascidian Holothuriada?, animals approach- 

 ing the Mollusca in their form, and having a soft circum- 

 scribed disk like the foot of a Gasteropodous Mollusc on 

 which the suckers are placed for progression. 2, The 

 Pentact^e, which have the suckers arranged in five regular 

 rows, and are more or less angular in form. 3, The 

 Thyones, which have the suckers scattered all over the 

 surface of the body ; and, 4, The Synapt^e, in which there 

 are no suckers on the body, the oral tentacula being the 

 only representatives of those organs. 



