ORDER TUBICOL^. 11 



M. de Lamarck distinguishes : 



Spirorbts, Lam., in which the branchial threads are 

 much less numerous, three or four on each side ; their tube is 

 a tolerably regular spiral, and they are usually very small *. 



Sa BELLA, CllV.,^ 



Have the same kind of body, and the same fan-like gills as 

 the Serpulae. But the two fleshy filaments adherent to the 

 gills both terminate in a point, and form no operculum ; they 

 are sometimes even entirely wanting. Their tube most fre- 

 quently appears composed of grains of clay, or very fine mud, 

 and is rarely calcareous. 



The known species are pretty large, and their branchial 

 plumes are delicate and brilliant in the extreme. 



Some of them, like the Serpulse, have a membranous disc on 

 the anterior portion of the back, through which pass the first 

 pairs of bundles of hairs. Their branchial combs are spirally 

 convoluted, and their tentacula are reduced to slight 

 folds X. ■ 



III. xvi. 7j and the Actinia or Animal-flower, Horn. Lect. on Comp. 

 Anat. II. pi. I. On this spiral convolution of the giUs, M. Savigny esta- 

 blishes his subdi\'ision of Serpulcs CymospircB, of which M. de Blainville 

 has since made a genus. Add. T. Stellata, Gm. Abildg., loc. cit., f. 5. re- 

 markable for an operculum formed of three plates strung together. 



* Serpula Spirillum. PaU. nov. act. Petrop. V. pl.V. f. 21. Serp. Spirorbis. 

 Mull. Zool. Dan. III. Ixxxvi. 1—6. 



f This name of Sabella designates in Linnaeus and Gmelin various 

 animals with factitious, and not transuded tubes. We confine it to those 

 which resemble each other in their proper characters. M. Savigny has 

 employed it as we have, with the exception of our first division, which he 

 places among his Serpulae. M. de Lamarck calls our Sabellag, Amphitritee. 



X M. Savigny leaves this division among the Serpulce, and makes of it 

 his Serpulce Spiramellce, of which M. de Blainville has since made his genus 

 Spiramella. 



