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Chiton squa?7tosiis Linne Squamose Chiton Southeast Florida and the West Indies. 2 to 3 inches in length. Color a dull, ashen-gray with wide, irregular, dull-brown, longitudinal stripes. Posterior edge of first 7 valves marked with 4 or 5 squares of blackish brown. Girdle with alternating pale stripes of grayish green and grayish white. Posterior valve with minutely pimpled ribs. Lateral areas of middle valves with 6 to 8 rows of small beads between which are microscopic pinholes. Central areas smoothish, with fine, transverse scratches. Common. Chiton viridis Spengler from the West Indies is very similar, but the margins of the central areas have 6 to 1 1 very short, wavy ribs, and the lateral areas have 3 or 4 strong ribs of rounded pustules. Uncommon. Chiton niarmoratus Linne Marbled Chiton South Florida to Texas and the West Indies. 2 to 3 inches in length. Color variable: (i) entirely blackish brown; (2) olive with flecks, patches and lines of whitish merging together towards the middle; or (3) purplish brown or light-olive with zebra-like stripes on the sides. Entire surface of valves smooth except for a microscopic, silky texture. Lateral areas a little raised. Underside of posterior valve with 14 to 16 slits. A common West Indian littoral species. Chiton laevigatus Sowerby Smooth Panama Chiton Gulf of California to Panama. 2 to 3 inches in length, similar to marmoratus. Girdle scales broader than high and not very glossy. Valves smooth, with a silky sheen and colored a grayish green over which are radiating rays of dark-brown. Similar coloration in the other valves. Underside of posterior valve with 2 1 narrow slits. Sutural plates on underside of middle valves with a dark blotch at the base. Common. Chiton albolineatus Sowerby (western Mexico, uncommon) is also a smooth species, but differs in having only 16 to 17 slits in the posterior valve and has snow-white, radiating lines on the lateral areas and on the end valves. The girdle scales are light blue-green and edged with white. Chiton virgulatus Sowerby Virgulate Chiton Magdalena Bay, Lower California, to Panama.