TEREBELLA. 211 



In as far as I have observed, the generic character may be found in 

 a vermicular annulate body, with pencils issuing from a number (perhaps 

 sixteen) of the upper segments ; numerous extensile, flexible tentacula ; 

 external ramified branchiae on the back of the neck ; the construction of 

 a tube, open at both extremities, so wide as to admit reversal of the 

 animal within. Specific distinction may be found in the configuration 

 of the branchiae, and in the quality of the materials for binding the 

 tube. 



