23 



edge by a fleshy collar, the lower extremity closed by 

 a membrane. The tube is encircled with strong an- 

 nular ribs separated into six compartments, or valves, 

 by longitudinal interstices. It is found buried in the 

 fat of whales, to the depth of several inches, its oper- 

 culum, and a portion of the upper part of the tube on- 

 ly visible on the surface. The number of additional 

 rings or circles which surround the tube, no doubt 

 mark its progressive growth, from the obvious neces- 

 sity of possessing an opening to the exterior, by keep- 

 ing pace with the increase of the substance in which 

 it is embedded. 



La Marck, in his generic description of this shell, 

 calls it an univalve, as he does his genus Balanus, ac- 

 counting for an increase of their size in circumference 

 by supposing that the pieces which are firmly fixed 

 together, may be disunited by the animal, the neces- 

 sary addition made to them, and again reclosed ; an 

 hypothesis extremely rational, but which appears to 

 militate against his assertion of these shells being uni- 

 valves. Another species has also been described by 

 Dr. Leach. 



Tubicinella balaenarium. 



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