SEDENTARI^T2 155 



Genus 4.— SERF UL A.— Zfi/«orc^. 



Generic Character. — Body tubular, elongated, depressed, and 

 attenuated behind ; segments numerous, and narrow ; small 

 bundles of awl-shaped bristles, in a single row on each side, and 

 also hooked bristles ; branchiae terminal, fan-shaped, and deeply 

 cleft into pinnated^, or plumose finger-like divisions ; mouth ter- 

 minal, placed between the branchiae, and surmounted by a pe- 

 dicled funnel, or club-shaped operculum ; tube solid, testaceous, 

 irregularly twisted, either grouped or solitary, fixed, with a round- 

 ed and terminal aperture. 

 Found solitary, or in groups curiously intertwined. 

 Serpula vermicularis. — The Vermicular Serpula. Plate 

 XIX. fig. l^. White, cylindrical, tapering, rugged, variously 

 curved and twisted. Inhabits the coasts of Britain. 



Genus 5 SFIRORBIS.— Lamarck. 



Generic Character. — Body tubular, subcylindrical, posterior- 

 ly attenuated ; six pinnated retractile branchiae, in radiated ex- 

 pansions, at the anterior extremity ; operculum placed between 

 the branchias ; tube testaceous, spirally twisted into an orbicu- 

 lar form or a horizontal plane, depressed and adhering below. 

 The aperture terminal and rounded or angular. 



Spirorbis nautioides.— The Nautilus- Shaped Spirorbis. 

 Plate XIX. fig. 15. White, nautilus shaped, transversely 

 wrinkled. One-eighth of an inch in diameter. Inhabits the 

 British coasts, on Algse, &c. 



TRIBE II AMPHITRIT^A. 



Branchiae not separate or covered by an operculum, and 

 disposed anteriorly ; tube membranous, or horny, and more or 

 less arenaceous. 



* With large branchiiB on tentacula. 



Genus 6.— AMFRITRITE.— Lamarck. 



Generic Character — Body tubicular, elongated, cylindrical, 



