6 TETEERES. 



pigmented (violet) rings, and two behind in process of formation. The fourth stage has 

 five to six segments ; the prostomial region is notably enlarged so that the larva is mushroom- 

 like. In the fifth stage the yellow pigment is greatly increased on the prostomium in 

 concentric rings, two eyes are on each side, long cilia occur on the border of the prostomium 

 and there are two palps with yellow pigment. The oesophagus has dense walls, whilst the 

 intestine is wide. Each segment has a belt of .violet pigment and touches of yellow 

 surround the anal region. The buccal segment has glandular bands ventrally and developing 

 tentacles; the following segment also has a glandular belt (in the fixed larva), latero- 

 ventrally a minute cirriform lobe and laterally three others. Four segments are furnished 

 with long and somewhat spatulate bristles corresponding with those pertaining to Tetreres, 

 Caullery. Above each is a minute tubercle, indicating the future branchiae. No ventral 

 bristles have appeared. The posterior segments clorsally bear hooks of the Sabellarian 

 type, and the anal ring of cilia is ornamented by touches of yellow pigment, and so 

 with the anal cone. 



Hacker 1 (1898) thought the Mitraria -larvae from the " Plankton Expedition " 

 pertained to the Hermellidas since the remarkable bristles were paddle-shaped at the tip 

 with a central spine like that seen in Sabellaria (Pallasia) Johistoni of the " Challenger." 



As noticed for centuries the Hermellids are conspicuous, both between tide-marks 

 and beyond it, by the formation of masses of firmly cemented sandy tubes, those of 

 S. spinulosa in the littoral region often covering large surfaces of rocks which have been 

 bored by P kolas, and thus to some extent preventing their rapid disintegration. In the 

 estuaries of English rivers entering the North Sea, as well as in certain Scotch bays, 

 8. alveolata, on the other hand, occurs in masses which are brought up from the bottom 

 by dredge or trawl, and called by the fishermen " Ross." Both species seem to range to 

 deeper water, S. spimdosa especially abounding on shells in Scottish seas. 



Genus OXXXII. — Tetreres, Caullery, 1913. 



Nereis, Pallas ; Terebella, Grmelin ; Hermella, Savigny, Schmarda ; Sabellaria, De 

 Blainville, Grube; Pallasia, De Quatrefages. 



Cephalic lobes form two elongated pillars pointed at their anterior ends. Dorsal 

 surface slightly concave, and each pillar has a row of more than twenty papillse on the 

 external margin, besides two rows of paleaa — external and internal. Paleas of the external 

 row more feeble and more numerous than those of the internal row, and both are sabre- 

 shaped with smooth edges. Inner and ventral surfaces of the cephalic lobes covered with 

 numerous tentacular filaments. Mouth ventral, between the cephalic lobes, surrounded 

 by a large hood (of upper and lower lips — Arnold Watson), its posterior border having ten 

 rounded cushion-like lobes, and laterally a much larger conical lobe, outside which is the 

 dorsal cirrus of the first segment. Tentacles (palps of some) two, on the dorsum of the lip, 

 D-shaped in section, grooved and crenate. Body of three regions, the anterior or " thoracic " 

 region having four setigerous processes on each side. Bristles long, hair-like, furnished with 



1 'Pelag. Polychset. u. Achsetenlar-ven, Plankton Exped./ p. 16, Taf. i, figs. 6 — 10, and Taf. ii, 

 figs. 11—13. 



