AMPHINOMIDAE. 23 



p. Body commonly filiform and most often colorless; palpi never 



biarticulate; tentacular cirri one or two pairs SijUidne. 



pp. Body typically short and plump and consisting of from twenty 

 to forty somites, rarely more, and often conspicuously colored; 

 palpi usually evidently, biarticulate; tentacular cirri from six 



to eight pairs, rarely two pairs or none Hesionidae. 



a. Prostomium more or less completely hidden by the peristomium; palpi greatly developed and 

 subdivided to form branchiae. 



Body subdivided into thorax and abdomen, with the notopodia of the abdomen bearing uncini. 

 6. With a pair of well-developed tentacles; peristomium very strongly developed and forming a 

 bilobed hood each lobe of which bears two or three semicircles of peculiar, stout, usually golden 

 yellow, setae or paleae, or these rarely almost obliterated; thorax of five or six somites. 



Sabellariidae. 



66. Tentacles very small; peristomium not of this form and without cirri or setae Serpuloidea. 



c. Nearly always with a well-developed thoracic membrane, formed by the fusion of cirri, and an 

 operculum; tube formed of mucin impregnated with calcareous matter, opaque, or rarely 



translucent Serpvlidae. 



cc. Without thoracic membrane and operculum; tube formed of mucin of variable consistence and 

 more or less transparent, strengthened or not with mud, sand, pieces of shell, or other foreign 

 material Sabellidae. 



Amphinomidae. 



The members of this family have most commonly an elongate body more 

 or less tetragonal in cross-section, less conmionly depressed and subelliptic 

 in outline. Colors nearly always brilliant, often showing as shades of green, 

 scarlet, violet, or yellow. 



The prostomimn is rounded and is bordered or almost surrounded by the 

 first somites. It bears a pair of palpi and one, three or five tentacles and may 

 or may not bear a dorsal caruncle or nuchal body. Eyes normally four but 

 sometimes two or wholly absent. 



The mouth is ventral in position and is somewhat removed from the ante- 

 rior end, being bordered by a number of the anterior somites. 



Parapodia biramous, with one or two dorsal cirri and one ventral cirrus 

 on at least part of them, though these may be rudimentary or absent on others. 

 Branchiae present, each a smgle, mostly arborescent or pennatifid tuft, never in 

 transverse series. 



Setae simple, capillary or sometimes as stouter hooked spines; in part 

 calcareous and as a result very brittle. 



Pygidimn with one or two processes which are but little developed; anus 

 dorsal, commonly large. 



Proboscis protrusible, bearing neither jaws, teeth, or papillae. 



The amphinomids, while occurring in the colder regions, apparently attain 

 their largest development in warmer parts of the world, such as the Polynesian 



