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ISCHNOCHITONIDAE 3 2
% 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.
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