Very small to medium-sized, depressed-trapezoid, later depressed lens-shaped shell with finely beaded spiral sculpture, very prominent peripheral keel, and extremely wide, funnel-shaped umbilicus, in which 2-4 fine spiral ribs are sunken; keel-forming lower peripheral rib spirally subdivided and consisting of inner part similar to upper peripheral rib, and outer part that bears coarse, flattened triangular nodules (which overlap onto the following whorl); midrib-area with 2-3 relatively fine ribs. Overall olive-brownish. Protoconch diameter 0.70-0.78 mm; almost planispiral, without anal keel. Teleoconch: very small to medium-sized, diameter of specimens in collections 4.2-12.4; mostly ca. 4 whorls. Shape: early stages depressed trapezoid, later depressed lens-shaped with very prominent peripheral keel and extremely wide, funnel-shaped umbilicus (UD ca. 54%, measured at basal keel). Sculpture consisting of beaded spiral ribs (larger specimens with many fine additional threads): Upper side: SSR distinctly separated, usually stronger than 2-3 MR (MR lacking on first whorl); Periphery: UPR strong, more prominent than SSR and MR; LPR distincdy divided into inner part similar to UPR and keel-forming outer part that is often spirally subdivided and bears coarse, flattened-triangular nodules (ca. 20 at 3 Tw, ca. 25 at 4 Tw); upper point of whorl attachment on lower side of outer part of LPR; weak "false suture* between UPR and LPR, here one (usually fine) additional spiral rib; Base: 3-4 relatively fine spiral ribs in area close to peripheral keel, followed by 3-4 wider spiral ribs (increasing in width towards umbilicus), the more coarsely sculptured innermost rib surrounding the umbilicus with a ± distinct basal keel; 2-4 additional, fine spiral ribs lowered into umbilicus. Coloration: overall olive-brownish. - Protoconch : small (0.70-0.78, x = 0.75), almost planispiral, without anal keel; whitish to yellowish-brown. - Periostracum and Operculum: as described for genus. - Radula and Anatomy: not known.

Granosolarium excavatum is similar, but has a much coarser shell sculpture, only one midrib, only one spiral rib on the umbilical wall and a distinctly larger (0.86) protoconch. Granosolarium asperum and G. elegantissimum lack the coarse, flattened triangular peripheral nodules, and have only one rib sunken into the umbilicus.

Geographical distribution: Eastern Indian Ocean (South Africa) and western Pacific (Indonesia, South China Sea, Philippines), and as Neogene fossil in Japan. Frequently listed (but never illustrated) in faunal lists of Recent Japanese mollusks; no Recent Japanese material studied.
Habitat: Sublittoral to upper bathyal (depth records between 15 and 494 m), live specimen from 462 m, sandy and muddy substrates.