Gafrarium divaricatum
Similar to Gafrarium dispar. Gafrarium divaricatum can be distinguished by its slightly more trigonal shape, and a stronger radial rib sculpture at the anterior end of the flank than that found on G. dispar.
Similar to Gafrarium pectinatum. Gafrarium divaricatum is distinguishable by its fine nodules that are equal in strength in all areas of the flank. G. pectinatum has more prominent nodules at the central area of the flank.
Similar to Gafrarium tumidum. Gafrarium divaricatum is distinguishable by its fine nodules that are equal in strength at all areas of the flank. G. tumidum has more pronounced nodules at the confluence of the central and posterior areas of the flank.
The overall shape is ovate. The anterior dorsal margin is straight, and the posterior dorsal margin is slightly convex. The valves are equal in shape and size (equivalve), and there is no gape when the valves are closed. Sculpture consists of growth lines, as well as comarginal and radial ribs that intersect to form very fine nodules on the anterior and most of the central area of the flank. On the posterior and part of the central area, there are oblique ribs. The radial, comarginal and oblique ribs meet at an area slightly posterior to the center of the flank, forming a tent-like pattern from the umbo to the ventral margin. The lunule is lightly impressed, defined by a fine shallow groove and extends half the anterior dorsal margin. There are no ribs present within the lunule. The umbo is slightly anterior and the beaks also point slightly to the anterior. The escutcheon extends half the posterior dorsal margin and is defined by a lack of ribs.
The exterior color is white or tan. Other external coloration varies; there may be areas of dark or light brown pigmentation, mottling, tent marks or stripes coinciding with the ribs. The interior is white. There may be dark brown pigment along all the margins or in the umbonal cavity, a posterior ray of purple and/or a purple blush along the pallial line.
The ligament is exterior, extends 1/4 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 most 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. There are very fine antimarginal crenulations on the ventral margin that match the external radial and oblique ribs; they become weaker at the anterior and posterior, and stop at the hinge plate. The posterior adductor muscle scar is slightly larger and rounder than the anterior, and the pallial sinus is absent.