Page:American Seashells (1954).djvu/406

areas greatly raised and with 2 convex, strong ribs of coarse beads. Anterior valve with 9 convex, beaded ribs. Posterior valve very high, convex and with 7 to 8 pairs of strong ribs. Interior bluish white. Girdle yellowish with reddish bands; thin, narrow and with microscopic, striated scales. Uncom- mon. Fa7nily CHITONIDAE Subfamily CHITONINAE Genus Chiton Linne 1758 Outer edges of insertion plates with tiny, sharp teeth or pectinations; girdle with small, hard scales that look like overlapping split peas; girdle colored with alternating bars of grayish green and black; interior of valves blue-green. Key to the American Chiton Valves entirely smooth: Girdle scales glassy; sinus of valves narrow . laevigatus (Pacific) Girdle scales dull; sinus of valves wide . marmoratus (Atlantic) Valves with sculpturing: Central area with longitudinal ribs: Posterior valve with round pimples . . tuberculatus (Atlantic) Posterior valve with radiating ribs . . virgulatus (Pacific) Central area smoothish and dull .... squamosus (Atlantic) Chiton tuberculatus Linne Common West Indian Chiton Plate id; figure 6-ji Florida to Texas and the West Indies. 2 to 3 inches in length. Color a dull grayish green or greenish brown. Some or all of the valves may have a smooth, dark-brown, arrow-shaped patch on the very top. Girdle with alternating zones of whitish, green and black. The scales are placed on the girdle, so that they appear slightly higher than broad, while in squamosus they appear to be broader than high. Lateral areas with 5 irregular, radiating cords. Central areas smooth at the top and with 8 to 9 long, strong, wavy, longitudinal ribs on the sides. End valves with irregular, wavy radial cords. Gills beginning at the juncture of the head and foot and with 46 to 48 lamellae. A very common species on wave-dashed, rocky shores.