[Illustration: FIG. 164.—_Aphrodite aculeata_ L. (from _Règne Animal_). Nat. size. _c_, Neuropodial chaetae; _p_, palps; 1, iridescent bristles; 2, stiff chaetae; 3, felting bristles of notopodium.] _Aphrodite._—The fifteen pairs of elytra, arranged as in _Polynoë_, are concealed by a "felting" of hair-like chitinous threads arising from the notopodium (Fig. 139, p. 268). _A. aculeata_ L.—The "sea-mouse" is one of the most beautiful of the Polychaetes. The small tentacle is very readily detached; the palps are very long; the parapodia of the peristomium are directed forwards so as to form lateral lips; and its cirri are not especially modified (see Fig. 132, p. 260). The body, which measures 3 to 6 inches, consists of thirty-five to forty segments, and is broadest in the middle, the last dozen segments being very small; the body terminates in a point. Some of the notopodial chaetae are brilliantly iridescent, and give the worm its characteristic coloration. It is fairly common in the coralline regions, and is frequently thrown ashore after storms. Atlantic and Mediterranean. In _Hermione_ the "felt" is absent, so that the elytra are exposed. _H. hystrix_ Sav. occurs in ten to thirty fathoms of water all over the British area and Mediterranean. It resembles in its general appearance a fat Polynoid, with strong chaetae. _Laetmonice filicornis_ Kinb. also occurs on our north-west coasts, and _L. producta_ Gr. has been dredged in 500 fathoms off the {313}west coast of Ireland; it has been recorded also from Kerguelen and from Japan, so that it has a very wide distribution.[373] Sub-Fam. 3. _Acoetina._[374]—The long, vermiform body has some thirty-nine to ninety-three pairs of elytra, placed on every alternate segment throughout. It is represented in the British area by _Panthalis_ from 75 fms., which forms a tube of black mud. Sub-Fam. 4. _Sigalionina._—This sub-family includes forms with a long, vermiform body; anteriorly the elytra are on alternate segments, up to the twenty-sixth, and posteriorly on every succeeding segment; "gills" here coexist with elytra; cirri are absent. The prostomium in _Sthenelais_ Kinb. has a median tentacle, which is absent in _Sigalion_ Aud. and Edw. _Sth. boa_ Jnstn. is common off our coasts near low-water mark, where it burrows in the loose sand with rapidity. It is an elegant worm, and may attain a length of 8 inches, though it is generally smaller; it is narrow, flat, and only slightly tapering at each end; the elytra, which may be more than a hundred pairs, are greyish or slightly brownish, some being lighter than others; the margin is fringed with simple processes (which in _Sigalion_ are pinnate). Atlantic and Mediterranean. In _Psammolyce_ the elytra are covered with sand grains. British and Mediterranean.