_Nerine_ is represented by two species, sometimes called "Ragworms." The genus is very similar to _Spio_, but the worms are of larger size. The prostomium is compressed by the forward growth of the peristomium, and appears as a ridge on the latter segment, extending downwards in front towards the mouth. The "gills" commence on the second segment, and are continued in every segment except the hindmost. _Nerine_ (_Scolecolepis_) _vulgaris_ Jnstn. is readily distinguished from other species by its somewhat T-shaped prostomium. It is an extremely common worm under stones and amongst seaweed at low water. It is some 3 or 4 inches in length and more slender than the following species. Its colour is yellowish-brown, and the red gills directed upwards and backwards give the appearance of oblique red lines. The podal membrane does not reach the tip of the gill. North Atlantic. It is {323}said to ascend rivers and live in brackish water. _N. coniocephala_ Jnstn. is much the same colour, but reaches a length of 8 inches, and a diameter of ¼ inch. The prostomium is conical. The podal membrane reaches to the tip of the gill in the anterior segments. The worm burrows rather more deeply and nearer low-water mark than the preceding species. FAM. 2. _Polydoridae._—_Polydora_ Bosc (= _Leucodore_ Jnstn.) is readily distinguished from the other Spionids, and, indeed, from any other Polychaet (except _Chaetopterus_), by possessing specially strong chaetae in the enlarged fifth chaetigerous segment. The anterior segments differ from the rest in the absence of gills and in the character of the chaetae (Fig. 133, A, p. 261). _P. ciliata_ Jnstn. inhabits soft mud tubes near low water; it also makes U-shaped galleries in stones and shells, and the tube projects from each mouth. The worm is about ½ inch long, consists of some forty segments, and is yellowish or flesh-coloured. The prostomium resembles that of _Spio_; the peristomium is raised into a slight collar at each side. The anus is surrounded by an incomplete funnel. The species has almost a world-wide distribution, having been recorded from Iceland, Australia, the Philippine Islands, as well as from the European seas. _P. coeca_ Oerst. often lives commensally with a sponge, having a protective odour.