340 



POLYCHAETA 



CHAR 



in formation, and has a circular aperture. The worm itself is 



The horny operculum is conical, with 

 its base upwards, fringed 



about lj inches long. 



with short processes. 20 

 fathoms in the North 

 Sea and Mediterranean ; 

 also from 275 fathoms 

 off the west coast of 

 Ireland. 



Pomatoceros triqueter 

 L. The white shell is 

 adherent, with a distinct 

 keel along its upper 

 surface ; the aperture is 

 overhung by a spine. 

 The tubes are abundant 

 everywhere, attached to 

 rocks, stones, shells, etc., 

 between tide-marks and 

 down to 18 fathoms. 

 The animal is very 

 handsome, the thorax 

 being deep blue, the 

 abdomen red in the 

 female, whitish in the 

 ripe male. The branchiae 

 are barred and spotted 

 blue, orange, and 

 white ; the operculum 

 is calcareous, and fur- 

 nished with a couple of horn-like processes. 



Filigrana implexa Berkeley is a small worm, but the slender 

 white tubes intertwine and adhere together in masses 3 or 4 

 inches high, occurring at low tide and down to 18 fathoms in 

 the North Sea and Mediterranean. The animal has only eignt 

 gill filaments on each side, one of which on each side is slightly 

 expanded to serve as an operculum. The worm multiplies by 

 transverse division. 



Spirorbis ~borealis Daudin is a still smaller worm, the tube of 

 which is coiled in a flat spiral about -^ to -- inch across ; it is 



Fig. 183. A group of tubes of Serpula vermicularis L. , 

 from the mouths of two of which the animals are 

 protruding, that on the right being seen from 

 above, br, The gill plume ; m, thoracic membrane ; 

 op, operculum ; op 1 , corresponding gill filament with 

 of the opposite side ; t, tube. (From Cuvier's 

 Regne Animal.) Nat. size. 



