Callista spuma
Similar to Callista planatella. Callista spuma has thinner, less prominent comarginal ribs than C. planatella. In addition, C. spuma has a more elongate lunule and a slightly more convex posterior dorsal margin. C. spuma also has interior purple coloration; whereas, C. planatella does not.
The overall shape is elongate, ovate. The anterior, ventral and posterior margins are rounded. The anterior dorsal margin is subconcave, and the posterior dorsal margin is subconvex. The valves are glossy, equal in size and shape (equivalve), and there is no gape when they are closed. Sculpture consists of growth lines and wide, rounded comarginal ribs. There are no ribs on the lunule or escutcheon. The lunule is spear-shaped, defined by a fine, shallow groove, and extends half the anterior dorsal margin. The umbo is anterior, and the beaks also point slightly to the anterior. The escutcheon is not well defined.
The exterior is white or tan with many brown radial stripes, and there may also be fewer, less noticeable comarginal stripes. The colors of the stripes deepens ventrally. There is typically brown-purple coloration at the posterior dorsal margin, and the lunule may be partially colored with purple pigmentation. The interior is white and there is typically purple coloration at the posterior and/or the anterior, concentrated along the margin and within the adductor muscle scars.
The ligament is external, extends 1/3 to half of the posterior dorsal margin and is supported by nymphal ridges. On the left valve, there are three cardinal teeth (2a, 2b, 4b), none of which are bifid. The anterior (2a) and central (2b) teeth are joined dorsally, forming an inverted "v" shape. The posterior tooth (4b) is fused with the nymph. There is also one anterior lateral tooth (A2) on the left valve. On the right valve, there are three cardinal teeth: the anterior (3a) and central (1) teeth are not bifid, and the posterior tooth (3b) is lightly bifid. There are two anterior lateral teeth (A1, A3) on the right valve, as well as a fine, weak ridge that runs parallel to the posterior dorsal margin. The anterior and posterior adductor muscle scars are similar in area, but the posterior is rounded, whereas the anterior is slightly more elongate. The pallial sinus extends to the middle of the nymph in length and forms an acute angle at its deepest point.