TUBICINELLA. 



end is closed according to Lamarck, h\ a mcmljranc : this 

 tube contains the animal : its opercuhim* composed of four 

 cqnal-sizcd, trapezoidal, obtuse, smooth and moveable 

 valves, smaller and rounded at their superior extremities, 

 is seen v^'ithin, near the edge of the exposed orbicular 

 aperture. Two of these valves of the operculum are pos- 

 terior, and the other two valves anterior: the membrane 

 v/hl^h lines this operculum is not tubular, but closed at tlic 

 b:vck, and open at the top and in front for the passai!;e 

 vf the amis or tentacula. 



We have ro]>resented a group of Tubicincllse in a 

 j»Drtion of the skin of a whale, lig. 1.; a single specimen 

 sliowing the outside of the tube, and the position of tiie 

 operculum, lig. 2.; and the four valves of the operculum, 

 i3g. 3. 



* We have not rojootcd tivc term, operculum, tbouirli it does not here seem 

 to us to he porrectly applied, ut least its application here does not accord M'ith 

 its general acceptation; but it is, perhaps, better to use it, because it is gene- 

 rally adopted, and is njoreovcr undei;;-tood, than to create a new term which 

 A'.ould o ;ly bo a-ddjag uuc to tUc many ditficultieo already attendant on concho- 

 -iQg'icai science. 



