198 POLYDORA OILIATA. 



In an interesting paper, Prof. Salensky l (1908) gives a description of the oesophageal 

 pouches of Polydora cornuta, Spio fuliginosus, etc., which he was led to examine from his 

 previous researches on Polygordius and Saccocirrus. In Polydora cornuta these are five in 

 number and well developed, though temporary (larval). He broaches the view that these 

 may represent the gill-slits of the Chordates and Enteropneusta. 



Polydora is a persistent borer in shells, aluminous shale, sandstone and other rocks, 

 and it especially frequents the valves of the oyster on every coast. 2 Mr. Crossland 

 found in the Red Sea that it inserted itself between the mantle and the large pearl shell, 

 where it accumulates mud in considerable quantity and makes it unsightly, the worm and 

 the mud being covered by a thin secretion of nacre. He thinks that it thus evades the 

 trouble of boring, but this is doubtful. M. Leon Vaillant, 3 again, uses the boring region 

 of Polydora in calcareous rocks as a limit. Where granite occurs they do not bore (De St. 

 Joseph). 



Polydoba oiltata. Plate LXXXIX, fig. 4; Plate XCIII, figs. 6 and 7 — young; Plate 

 XCVII, fig. 7— Infusorian parasite; Plate XCVIII, fig. 15— tail; Plate XCIX, figs. 

 1 and 1 a — tubes and tentacles ; Plate CVI, figs. 2 — 2 d — bristle and hooks. 



Specific Characters. — Head with the prostomium elevated and terminating anteriorly 

 in two rounded lobes with a median notch, and the ridge passes backward to the third 

 segment. Dark pigment at the sides of the ridge and in the furrows of the first four 

 segments. Four black eyes on the ridge. Body largest in the anterior third, flattened 

 dorsally and rounded ventrally, tapered a little anteriorly and more distinctly posteriorly, 

 where it ends in a cup-like process with diminished margins trending to a dorsal notch. 

 Segments from sixty to seventy-five. Colour yellowish-brown or straw-yellow, with the red 

 median dorsal vessel. Branchiaa commence on the seventh foot and extend to the thirty- 

 eighth, though the number varies. First foot with a dorsal lamella without bristles, but the 

 latter occur throughout the rest of the body. The fifth bristled segment has large hook-like 

 bristles, the tips being curved, more or less acute, and having a small spur on the neck. 

 They are directed backward or upward. 



Synonyms. 

 1778. Scolopendra marina, Slabber. Naturkund. Verlustig., p. 51, pi. vii, figs. 1 and 2. 

 1781. Insecte destructeur des pier res, Dicquemare. Obs. sur la Physique, t. xviii, pp. 222 — 224, pi- ii- 

 1802. Polydora cornuta, Bosc. Vers, i, p. 150, t. iii, figs. 7 — 8. 

 1815 ? „ „ Oken. Lehrbuch, iii Theil, ii Bd., p. 374. 



1827 ? Spio caudatus, Delle Chiaje. Mem., vol. ii, p. 426, Taf. xxviii, fig. 10. 

 1828. Spio seticornis, Blainville. Diet. Sc. nat., Vers, t. lvii, pi. xix. 

 1836. „ calcarea, Templeton. Loud. Mag. Nat. Hist., vol. ix, p. 234, fig. 27. 



„ Diplotus sp. ? Garner. Trans. Zool. Soc., vol. ii, p. 95. 

 1838. Leucodore ciliatus, Johnston. Mag. Zool. and Bot., ii, p. 67, pi. iii, figs. 1 — 6. 



1 'Bull. Acad. Imper. St. Petersburg/ pp. 687—708, with text-figs. 



2 Vide "On the Boring of Certain Annelids," ' Ann. Nat. Hist./ Oct., 1868, pp. 276—295, pis. 

 xviii, xix, and xx ; and " On the Boring of Polydora in Australian Oysters," Idem, April, 1902, p. 308. 



3 < Ann. Sc. nat./ 7 e ser., t. xii, pp. 39—50, 1891. 



