The chitons' eight plates differentiate them from all other molluscs. These omnivores spawn grey-green eggs, and fertilization occurs externally. Miniature adults form by sixteenth day.
The underside of this species is composed of a flat foot with a row of gills along each side (gills not visible in this photo). The edges of the mantle form a wide belt around the foot. Photographed by Dave Cowles at San Simeon, CA 1995
The head plate (plate 1, seen here) is about the same width as plate 8, and the girdle is about the same width in front as on the sides. The girdle has neither scales nor tubercles, but it does have fine, scattered hairs which are so fine and sparse that it is hard to see them except along the edges.
Another photo of the underside. Photo by Dave Cowles, San Simeon, CA April 1997 This species was formerly abundant at San Simeon, CA. During the latter years of the 1990's I (Dave Cowles) observed large numbers decomposing and washing up onto the beach. I suspect a disease was affecting them. Those washing ashore were blotched, as some living individuals are. I wonder if the blotching seen in living individuals is a sign of disease? Far fewer can be found there now.
The girdle hairs are sparse and fine. They can hardly be seen except, for example, here along the edge of the mantle at high magnification. The fine filaments which sprout from the hairs are often in two rows of curved, diverging bristles on opposite sides of the main hair and have a glassy spicule on the end. Photo by Dave Cowles, August 2012
