Page:American Seashells (1954).djvu/403

Rh % to /4 inch in length, oval. Moderately sculptured and without very distinct lateral areas. It has microscopic, even, quincunx pittings on the upper surfaces of the valves. End valves with concentric rows of fine, low beads. Lateral areas with fine, wavy, longitudinal, incised lines. Posterior slope of posterior valve is concave and with 9 slits. Color whitish with heavy mottlings of olive-green; rarely with white spots. Girdle narrow, colored with alter- nating bars of white and greenish brown. Scales like microscopic split peas which are finely striated. A fairly common shallow-water species. Ischnochiton magdalenensis Hinds Magdalena Chiton Coos Bay, Oregon, to Lower California. 2 to 3 inches in length, elongate. Color a drab greenish, commonly whitish due to wear. Central areas with fine, irregular, longitudinal cuts and with diamond-shaped pits near the lateral areas. Lateral areas prominently raised and with 10 to 12 coarse, radial ribs of gross, low beads. Front slope of anterior valve straight. Interior of valves bluish with the posterior end of each whitish. Girdle rather narrow and with alternating, faint bars of brown and yellowish brown. Scales round and so small that the girdle has the texture of fine sandpaper. Common. Ischnochiton conspicuus Pilsbry Conspicuous Chiton San Miguel Island, California, to the Gulf of California. 2 to 6 inches in length, very similar to magdalenensis, but the front slope of the anterior valve is very concave; the central areas are practically smooth and with flecks of green. Scales are elongate, hard, and so densely packed that the girdle feels velvety. Interior of valves pinkish and blue. Moderately common between tides. Ischnochiton acrior Pilsbry Acrior Chiton San Pedro, California, to Lower California. 2 to 6 inches in length, very similar to magdale7iensis. Instead of dia- mond-shaped pittings on the sides of the central areas, there are wavy ribs. The front slope of the anterior valve is very concave, as in conspicuus. The scales are similar to those in inagdalenensis, but much larger. Interior of valves pinkish with a blue spot at the anterior end of each valve. Moderately common.