Original description, by Linnaeus (1758, p. 689):
"V. testa sublentiformi sulcis longitudinalibus rugosis: pube antrorsum ramosa.
Rumph. mus. t. 42. f. D.
Gvalt. test. t. 72. f. F. E.
Argenv. conch, t. 24. f. P.
Habitat in Indiis."
Similar to Gafrarium divaricatum. Gafrarium pectinatum has more prominent nodules at the central area of the flank and no comarginal ribs; whereas, G. divaricatum has nodules of even strength throughout the flank and comarginal ribs.
Similar to Gafrarium tumidum. Gafrarium pectinatum is distinguishable by its more rounded posterior margin and less inflated valves. G. tumidum has a flattened posterior margin and is more inflated.
The overall shape is ovate. The anterior dorsal margin is nearly straight, and the posterior dorsal margin is slightly convex. 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. Near the confluence of the posterior and central areas of the flank, some of the oblique lines of nodules are split from the most posterior radial line of nodules. Not all oblique lines meet the posterior radial line. The nodules may become weaker near the ventral margin. The lunule is lightly impressed, defined by a fine shallow groove, lacks ribs and extends 1/3 of the anterior dorsal margin. The umbo is anterior and the beaks also point slightly to the anterior. The escutcheon is lightly impressed and lacks ribs or nodules.
The exterior color is white. There may be light brown mottling, tent marks and/or comarginal stripes. The lunule may be darkly pigmented. The interior is white and may have dark purple coloration on the nymph, as well as under it.
The ligament is external, extends 1/4 of the posterior dorsal margin and is supported by nymphal ridges. On the left valve, there are three cardinal teeth. The anterior tooth (2a) is not bifid, the central tooth (2b) is lightly bifid, and the posterior tooth (4b) is not bifid and 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 crenulations on the anterior and ventral margins that match the external sculpture; the crenulations are strongest at the posterior of the ventral margin, and gradually become weaker. The posterior adductor muscle scar is larger than the anterior. The pallial sinus is absent.