Gafrarium tumidum
Similar to Gafrarium divaricatum. Gafrarium tumidum can be distinguished by the more pronounced nodules at the confluence of the posterior and central areas of the flank.
Similar to Gafrarium pectinatum. Gafrarium tumidum is distinguishable by its flatter posterior margin and more inflated valves.
The overall shape is ovate. The posterior margin is subtruncated. The anterior dorsal margin is subconcave, and the posterior dorsal margin is subconvex. The valves are equal in size and shape (equivalve), and there is no gape when they are closed. Sculpture consists of growth lines, radial lines of nodules on the anterior and central areas of the flank, and oblique lines of nodules on the posterior area of the flank. The lines of nodules may split as the animal grows, resulting in more lines of slightly finer nodules at the ventral margin. The radial lines of nodules become more pronounced with stronger nodules and wider interspaces near the confluence of the central and posterior areas of the flank. At the posterior, some of the oblique lines of nodules are split from the most posterior radial line of nodules. Not all oblique lines may meet the posterior radial line. The lunule is lightly impressed, defined by a fine shallow groove and extends half the anterior dorsal margin. There are no nodules within the lunule. The umbo is anterior and the beaks also point slightly anteriorly. The escutcheon is lightly sunken and defined by a lack of nodules; it extends 3/4 of the posterior dorsal margin.
The exterior color is white, light tan or brown. Other coloration is highly variable, but may include a dark brown or golden mottling of the nodules, dark pigmentation at the posterior dorsal margin, and purple coloration at the lunule and/or escutcheon. The interior is white with purple coloration at the posterior dorsal margin, and sometimes also the anterior dorsal margin. The purple descends from underneath the nymph and the lunule, and sometimes covers the posterior and anterior adductor muscle scars.
The ligament is external, extends 1/3 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 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 (3a, 1, 3b), none of which are bifid. There are also two anterior lateral teeth (A1, A3) on the right valve. A weak ridge runs parallel to the posterior dorsal margin in both valves. There are crenulations on the ventral margin that coincide with the sculpture of the flank. They are weak at the anterior and become gradually stronger. At the posterior end of the ventral margin, the crenulations result in a strong wave-like pattern of the commissure. The posterior adductor muscle scar is slightly larger and rounder than the anterior, and the pallial sinus is extremely shallow.