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 MARINE ZOOLOGY matic. Length I i-2 inches. In sand. Cromer (P.). 10. Ammotrypane aulogaster, Rathke. Like the preceding, but more cylindrical ; gills on all segments ; sides of body ridged, ventral surface grooved. In sandy mud. Recorded from deep water. Silver Pit (P.). 1 1 . Arenkola marina^ Linn. The common ' lug- worm.' Gills, 12 or 13 pairs, red, arborescent, forming tufts on the middle segments. Hasborough (R, A. Todd). 12. Praxilla pratermissa, Malmgren. Head with an oval membranous rim, incised at 3 points ; segments 26, the last 5 with- out foot-bristles ; anal segment with a circlet of 22-33 cirri, one being longer than the rest. No gills. Colour pale ochre. Length 4^ inches. OfF Hasborough, in mud (tubes ?) (P.). D. Tube-building Worms * I. Terebellida. Head bearing a tuft of flexible filiform ten- tacles, and succeeded by 1—3 segments bearing short tufts of gills. 13. Lan'tce conchilega. Pall. The common ' sand-mason * ; length 3-6 inches. Gills arborescent. Tube made of agglutinated particles of shell, pebbles, etc. ; it is buried in sand except a short terminal portion which protrudes and bears a charac- teristic fringe of sandy threads. Hasborough (R. A. Todd), Yarmouth (Harmer). 14. Thelepus cincinnatus, Fabr. Length 2-4 inches, reddish, with a reti- culate pattern on the back. Gills unbranched, in transverse rows, on 3 segments. Tube thin, adherent by its whole length to shells, etc. Off Yarmouth, common (P.). II. Auricomata. Tentacles numerous but short ; head pro- vided with large golden bristles ; hinder part of body different from the front. 15. Pectinar'ta auricomay MUll. Head-bristles forming a pair of straight combs, set in a line ; shortly behind these is a low membranous collar with a dentate margin. • Some of the Nereids also secrete tubes, but do not build them with foreign particles. 83 Tube smooth, conical, slightly curved, open at both ends ; made of sand-grains cemented together. Length i| inches. Cromer (Gel- dart). 16. Pectinaria helgica, Pallas. Differs from the preceding in having a smooth margin to the membranous collar, and builds a straight tube. Common in sand-flats, in which it burrows head-first (probably with its combs). 17. Sabellaria alveolata (Linn.). Head-bristles forming a complete crown, and composed of three series on each side, those of the innermost series pointing inwards, the rest outwards. Outermost bristles palmate, and armed with 5-7 smooth curved prongs at their tips. Tubes made of course sand-grains ; generally aggregated in large irregular masses near low-water mark. Reported abundant off Cromer, Hasborough and Yarmouth (P.), but possibly confused with the next species. 18. Sabellaria spinulosa (Leuckart). The outermost opercular bristles have the central prong greatly elongated and spinous. Below low-water mark. Abimdant off Yar- mouth (S. F. Harmer). III. Sabellida. Head surrounded by a collar and bearing a wreath of feathery gill-plumes, in two lateral halves. 19. Sabella penicillus, hinn. Length lo or 12 inches. Gill-plumes i^ inches long, spotted with purplish brown. Labial tentacles 2, conical. Tube straight, slender, made of fine mud, and deeply im- bedded in the same material, at or below low- water mark. Yarmouth (Harmer). 20. Serpula triquetra (L.), MSrch. One of the labial tentacles is modified into a calcareous operculum, furnished with a couple of horn-like processes. Tube thick, white, calcareous, keeled, adherent along its length to stones, shells, etc. Length i^ inches. Off Cromer and Hasborough, fairly common (P.). 21. Filograna impUxa, Berkeley. Length ^-| inch. Gill-plumes 8 on each side, one of which on each side is slightly ex- panded to serve as an operculum. Tubes white, calcareous, very slender, intertwining in masses 3 or 4 inches high. Off Hasborough, common (P.), Yarmouth (Harmer).