30 CLASS ANNELIDA. 



HYPOGiEON, Sai\, have an additional odd pair of setae on 

 the back of each ring : they belong to America. Hypogceon 

 hh'tum, Sav., Egg. Annel. p. 104. 



MM. Audouin and Milne Edwards also distinguish Tro- 

 PHONIA, which have on each ring four bundles of shorter 

 setae, and a great number of long and brilliant ones, which 

 suiTound the mouth.- — TropJionia barhata, Aud. and Edw. 

 Littor. de la France, Annel. pi. x. f. 13 — ^b. 



Nais, Linn., 



Have the body elongated, and the rings less marked than the 

 lumbrici. They live in holes, which they excavate in mud, 

 at the bottom of the water, and from which they protrude the 

 anterior part of their body, which they keep incessantly mov- 

 ing. There are visible on the head of many some small black 

 points, which may be taken for eyes. They are small worms, 

 and their power of reproduction is as astonishing as that of 

 the hydrae. Many of them exist in our fresh waters. 



Some have setae tolerably long, Nais Elingius, Mull. Wurm, 

 ii ; N. littoralis, id. Zool. Dan. Ixxx. 



And sometimes a long proboscis in front, Nais proboscidea, 

 id. Wurm, i. 1 — 4., of which M. de Lamarck makes his genus 

 St YL A HI A. 



Or several small tentacula at the posterior extremity, Nais 

 digitafa, Gm. ; coeca. Mull. ib. v. ; of which M. Oken makes 

 his genus Peoto. 



Others have very short setae, Nais vermicnlaris, Gm., Roes. 

 HI. xciii. 1 — 7 ; A^. Serpentina, id. xcii., and Mull. iv. 2 — 4 ; 

 Lumbricus hibifex, Gm., Bonnet, vers d'eau douce, iii. 9 — 10. 

 Mull. Zool. Dan. Ixxxiv. ; Lumh. lineatus, Mull. Wurm. iii. 

 4—5. 



We may approximate to this genus certain annelida hitherto 

 referred to the lumbrici, which fabricate for themselves tubes 

 of clay, debris, &c., in which they live, Lumbricus iubicola, 



