Sub-Fam. 1. _Polynoina._—Body flattened, with nearly parallel sides, usually short, more rarely worm-like; three tentacles; peristomium with long dorsal and ventral cirri; the ventral cirri of the next segment are also elongated. Jaws are present. Elytra, usually twelve to eighteen pairs, the surface of which is more or less papillose, and may be "fringed" along the outer border, with long processes. The colouring of the elytra is characteristic in most cases, though liable to considerable variation in some species. The chaetae are generally strong, and of bright golden colour: they are all unjointed. The _Polynoina_ are generally but feeble swimmers, {310}and are mostly found under stones at low tide. Some species have a very wide geographical range. _Polynoë._[370]—The body is short; none or only a few segments at the end of the body are uncovered by the elytra, except in the long body of _P. johnstoni_. _A. With twelve pairs of elytra._—In _P. squamata_ Linn. the elytra entirely cover the body and conceal the head, each elytron overlapping the next posterior one, and those of the two sides overlapping. General colour sandy-brown, speckled, lighter or darker. The fringed elytra are very firmly fixed to the body. The notopodial chaetae scarcely project from below the elytra. The worm is common between tide-marks and in the coralline region, is about one to one and a half inches in length, and about one-third of an inch in width. Atlantic. _P. clava_ Montagu, may attain a larger size, though it is generally smaller. The elytra are dark, usually grey, mottled with white or light grey, unfringed, and do not overlap to so great an extent as in _P. squamata_, so that the middle of the back and the hinder part of the body is more or less exposed. This is never the case in the preceding species, but even here it is subject to variation in extent, depending on the amount of food contained by the worm or on the ripeness of the genital products. It occurs in the Mediterranean.[371] [Illustration: FIG. 162.—Elytra, A, of _Polynoë squamata_ L.; B, of _P. clava_ Mont. × 10. _a_, Area of attachment; _e_, external margin; _f_, fringe (the letter is at the posterior side of the elytron); _i_, internal margin. (From Bourne.)]