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320 Figure 68. Common Eastern Chiton, Chaetopleiira apiculata Say, Yo inch.

areas with 15 to 20 longitudinal rows of raised, neat beads. Lateral areas distinctly defined, raised and bear numerous, larger, more distantly spaced beads which may or may not be present on the more dorsal region. Interior white or grayish. Slits of anterior valve 11, central or middle valves i, posterior valve 9 to 11. Girdle narrow, mottled cream and brown, microscopically granulose and with sparsely scattered, transparent, short hairs. 22 to 24 gill lamellae in each gill which start just be- hind the juncture of the head and foot and extend all the way back to the posterior margin of the mantle where there is located a small, single-lobed lappet. Common from I to 15 fathoms. In the north, the exterior color is buff to ashen, rarely reddish. On the west coast of Florida, where they are commonly found attached to Finna shells, the colors vary from light-gray, mauve, yellow to white, and are commonly with a darker or lighter streak down the center or rarely with longitudinal blue stripes. Genus Ischnochiton Gray 1847 Subgenus Stenoplax Carpenter 1878 Ischnochiton floridanus Pilsbry Florida Slender Chiton Miami to Dry Tortugas, Florida. I to 1 34 inches in length, about 3 times as long as wide, elevated, with the valves roundly arched, not carinate. Color whitish to whitish green with markings of olive, blackish olive or gray. Lateral axeas raised and with wavy, longitudinal riblets which are commonly strongly beaded. Central areas with wavy, longitudinal ribs. Interior of valves mixed with white, blue and pink, rarely all pink or all white. End valves concentrically (or rarely axially) beaded. Intermediate valves with i slit, posterior valve with 9. Girdle marbled with bluish and gray, and densely covered with round, solid, finely striated scales. Moderately common. Ischnochiton purpmascens C. B. Adams (Purplish Slender Chiton) from the West Indies is very similar, but the end valves and lateral areas have smooth, instead of beaded, wavy, concentric riblets. Common. Ischnochitoji papillosus C. B. Adams Mesh-pitted Chiton Tampa to the Lower Keys and the West Indies.