SABELLIDES AND SERPULIDES 



221 



type ; and one of the Bermuda species (^P. bermudensis sp. nov.) 

 having nearly straight regularly tapered setae similar to those on the 

 thorax, with deeply serrate edges and still different uncini, is made the 

 type of another new genus, Paravermilia, The thoracic setae in all 

 three forms are regularly tapered, differing only in their comparative 

 length and breadth ; the opercula are also alike in having a horny or 

 chitinous end which varies greatly in form. In the Bermuda species it 

 forms a high, irregularly bent or curved tapered cone made up of sev- 

 eral unequal parts which fit on to each other, resembling a spiral shell. 



The uncial plates in the numerous forms belonging to this family 

 show great variability in form, are often very irregular in outline, 

 but the opposite sides stand in definite relation to each other so that 

 ' tetragonal,' ' rectangular,' ' rhomboid' and ' trapeziform' have been 

 adopted for them in the following table. 



ANALYTICAL TABLE FOR SERPULA AND RELATED GENERA. 



I. With an operculum 2. 



Without an operculum (see p. 226) 14. 



a. One or more entire branchiae differentiated into or replaced by a peduncle 



bearing an operculum 3. 



2''. Tip only of one or more branchiae differentiated into an operculum-like 



organ (see p. 226) 11. 



3. Operculum furnished with a calcareous plate 4. 



Operculum furnished with a chitinous or horny plate (see p. 223) 8. 



4. Collar setae present 5. 



4'. Collar setae absent. 



(i) Placostegus Philippi 1844. 



Type, P. tridentatus (Fabricius 1779, as Serj)tila, -f- Gunnerus 1768, 

 figure, as Serfula triquetra, + Philippi 1844, figure, as P. crystalltna) 

 Morch 1863, as first species, also as P. tricuspidaius^ + Levinsen 

 1883, figures, + Marenzeller 1893, figures. North Atlantic Ocean, in 

 20-200 fms. 



Uncial plates rectangular in form, with very numerous fine appressed 

 teeth, the lowest large and fang-like. Operculum with calcareous plate. 



(2) Placostegopsis Saint-Joseph 1894. 



Type, P. lajtgerkansi (Marenzeller 1893, as /'/acc5/^^«5, -f Langer- 

 hans 1883, figures, as Placostegus trtcusptdatus, non Sowerbj) Saint- 

 Joseph 1894. Madeira, Atlantic Ocean. 



Uncini similar to those in Spirorbi's. Operculum with a simple cal- 

 careous plate. 



5. Superior setae not simple tapered blades 6. 



5'. Superior setae simple tapered blades. 



(3) Dasynema Saint-Joseph 1894. 



Type, D. chrysogyrus (Grube 1878, figures, as Serptcla) Saint-Joseph 

 1894. Philippine Islands, Pacific Ocean. 



