Ventral and dorsal view of foot with viscera and girdle removed. Orkney, Scotland. February 2015. Leg. P. Lightfoot per J. Porter.
1:strong transverse foot muscles provide firm grip of substrate.
2: strong, lateral longitudinal muscle (almost hidden by ‘3’, part missing at anterior left) encircles the entire body passing under the outer margins of the valves. Used for defensive curling of body
3: lateral muscles connect the foot to the ends of the valves. These and other muscles attached to the valves enable shell articulation to conform closely to uneven rock surface.
4: ctenidia (gills).

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