_Myrianida fasciata_ Milne Edwards, with its foliaceous cirri, occurs off our coasts (see Fig. 149, p. 280). Atlantic, Mediterranean. FAM. 2. _Hesionidae._—The body is relatively short, with only a few segments (sixteen to fifty, according to the genus); in the larger forms it is cylindrical. The parapodium is usually uniramous; the dorsal cirri are long and multiarticulate; the chaetae are jointed. The prostomium carries, in addition to four eyes, two or three tentacles, and generally a pair of jointed palps. The peristomium and two or more of the following segments are achaetous, and carry long "peristomial" cirri. The pharynx is very long but unarmed. _Psamathe_ Johnston, has many segments; head with two tentacles and a pair of three-jointed palps. _P. fusca_ Jnstn. occurs amongst coralline Algae, to which it bears some resemblance, which is heightened by the moniliform cirri. It is a small worm, less than an inch in length. Mediterranean. _Castalia punctata_ Müll. is dirty green or brownish, with a narrow purplish band on each side. It occurs in deeper water than the preceding. In _Ophiodromus_ the head has three tentacles; the palps are two-jointed; there are six pairs of peristomial cirri; the parapodia {309}are biramous. _O. vittatus_ Sars is dredged in numbers off the Scotch coast, and is found also at low tides. It measures 2 inches in length. A closely allied species lives in the ambulacral grooves of the starfish _Astropecten_. FAM. 3. _Aphroditidae._[369]—The most characteristic feature of this family, and one by which its members are absolutely distinguished from all other Chaetopods, is the possession of scales or "elytra" on the back. These flattened dorsal cirri are of a somewhat horny texture, and are carried, generally, on alternate segments of the body; filamentous cirri occurring on the other segments. In the sub-families _Hermionina_ and _Polynoina_ the elytriferous segments are 2, 4, 5, 7, 9, etc., up to 23; then every third segment. The worms are usually short, with some thirty-five to forty-five segments, though _Sthenelais_ and a few others have many more. (For head see p. 262, and for parapodium see pp. 265, 268.) The pharynx is very thick walled, and furnished with two pairs of jaws, which are, however, not hardened in the sub-family _Hermionina_. The intestine is provided with a number of paired longer or shorter caeca (Fig. 142). A considerable number of this family are commensal or parasitic (see p. 297). The family is well represented on our own coasts, so that only a few of the more readily distinguishable species can be here described. [Illustration: FIG. 161.—_Polynoë squamata_ L. Nat. size. _c_, Notopodial cirrus; _e_, elytron; _f_, parapodium; _p_, palp; _t_, tentacle. (From Johnston.)]