176 SEDENTARIA. 



tal plane, depressed and adhering below. Tlie aperture ter 

 minal and rounded or angular. 



Spu^orbis nautiloides The Nautilus-shaped Spir- 



ORBis. Plate XIX. fig. 15. White, nautilus-shaped, trans- 

 versely wrinkled. One-eighth of an inch in diameter. In- 

 habits the British coasts, on Algse, &c. . 



TRIBE II. AMrniTKlTJiA. 



Branchiae not separate or covered by an operculum, and 

 disposed anteriorly ; tube membranous, or horny, and more 

 or less arenaceous. 



* With large brancliiie on tentacula. 

 Genws 6. -AMPHITRITE Lamarck. 



Generic Character. — Body tubicolar, elongated, cylin- 

 drical, attenuated behind, with many annulated segments ; a 

 single row of setiferous papillae; subulate, fasciculate bristles 

 and hooked setae; branchiae in slender finger-shaped fasciculi, 

 disposed like a fan, and spreading into a disk ; two short 

 subulate filaments inserted at the internal base of the 

 branchiae, between which is a terminal mouth ; tube elon- 

 gated, cylindrical, tapering towards the base, membranous or 

 coriaceous, and generally naked. 



Awphitrite ventilahrum. — The Fan Amphitrite. Plate 

 XIX. fig. 19. Tube tapering, incurved, and smooth; of a 

 cream yellow colour. Inhabits the Mediterranean sea. 



Genus 7.— TEREBELLA—ZamarcA. 



Generic Character. — Body tubicolar, elongated, cylindri- 

 cal, attenuated posteriorly, segments transverse, and sub- 

 annulated ; having a row of nodulous and setiferous papillae 

 on each side; with numerous filiform, twisted tentacula sur- 

 rounding the mouth, and terminating in front of it; two rows 

 of ramose branchiae placed in a single row beneath the tea- 



