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Rh center of each valve. Girdle may have widely scattered tufts of hair. In- terior of valves white. Common from 5 to 30 fathoms. S. pallasi Middendorff (Concealed Pacific Chiton) is very similar to vestitus, but the girdle is much thicker and the bunches of reddish hairs more numerous. Uncommon from 3 to 10 fathoms.

Figure 66. Pacific Coast chitons, a, Placiphorella velata Pilsbry, i to 2 inches (California); b, Katharina timicata Wood, 2 to 3 inches (Pacific Coast); c, Syjn- metrogephynis vestitus Brod. and Sby., i to 2 inches (Arctic waters to Massa- chusetts and Alaska); d, Amicula stelleri Midd., 6 to 12 inches (Pacific Coast), showing position of the ist and 7th valves only. Genus Ceratozona Dall 188: Ceratozona rugosa Sowerby East Florida to the West Indies. Rough Girdled Chiton Figure 67a I to 2 inches in length, oblong, slightly beaked. Surface commonly eroded, whitish gray with blue-green to moss-green mottlings on the sides of the calves. Surface roughly sculptured. Anterior valve with 10 to 11 strong, rugose, radiating ribs. Lateral areas bounded in front and behind by a large, rugose rib. Central area with low, rough, longitudinal ribs. In- terior of valves bluish green. Girdle leathery, yellowish brown and with numerous, yellowish brown clusters of strap-like hairs. Posterior valve rather small and with 8 to 10 slits. 35 to 36 gill lamellae. The gills extend the length of the foot, but do not go as far as the posterior end. Very common, especially in the Greater Antilles. Family CRYPTOPLACIDAE Genus Cryptoconchus Burrow 1815 Cryptoconchiis floridanus Dall Southeast Florida to Puerto Rico. White-barred Chiton Figure 67b Rarely over an inch in length, long and narrow, and characterized by its thin, black, naked girdle which extends on to the valves except over the narrow, beaded dorsal area. These exposed bands in the valves make