Medium-sized, depressed bell-shaped shell with beaded spiral sculpture, very promi¬nent peripheral keel, and very wide, funnel-shaped umbilicus, in which one fine spiral rib is 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 following whorl; midrib-area with only one rib. Yellowish-brown with peripheral keel lighter-colored. Protoconch diameter 0.86 mm, weakly heterostrophic, without anal keel.
Teleoconch: medium-sized (11.4 at 5 Tw). Shape: depressed bell-shaped, with very wide, funnel-shaped umbilicus (UD ca. 42% SD). Sculpture: consisting of beaded spiral ribs; Upper side: SSR about as strong as UPR, one rib in MR-area; Periphery: UPR about as strong as upper part of LPR; LPR distinctly divided into inner part similar to UPR and keel-forming outer part that is spirally subdivided and bears pointed, flattened triangular nodules (ca. 23 at 4 Tw); upper point of whorl attachment somewhat below outer part of LPR, therefore LPR-nodules overlapping onto following whorl; after 2 1/4 Tw, one additional spiral rib between UPR and LPR; Base: 1-2 fine spiral ribs in area close to periphery, followed by four distinct spiral ribs (increasing in width towards umbilicus), of which the more coarsely sculptured innermost surrounds umbilicus (with ± distinct central groove on umbilical side); an additional spiral rib (the weakest on the base) sunken into umbilicus, to about 2/5 of whorl height Coloration: early whorls mauve-brown, later yellowish-brown; LPR with peripheral nodules lighter colored. - Protoconch: small (0.86), weakly heterostrophic, without anal keel; yellowish. - Periostracum, Operculum, Radula and Anatomy: not known.

Granosolarium excavatum is to date only known from a single specimen. The different shell sculpture, especially the combination of only one midrib, flattened-triangular nodules on the periphery and one weak rib sunken into the umbilicus, separate it clearly from its known congeners. The closest form is G. mirabile.

Known only from the type locality in the Hawaiian Islands.
Habitat: One empty shell was dredged from fine sand in 309-333 m depth