Shell shape variable, slender to cylindrically ovate (SL to more than 60 mm). Spire height and profile variable, profile usually slightly concave. Spire callus almost entirely covering spire whorl, cream yellow to greyish white and sometimes with purplish tint. Cloak colour variable, usually very light to dark yellowish cream, with brown to bluish grey, often very hazy and indistinct, reticulated pattern. Fasciolar band white to pale orange, with distinct brown flammules or blotches.
Anterior band with brown blotches, often forming an interrupted line just anterior of the raised cord-like rear edge. Parietal callus white, very swollen posteriorly in large specimens; occasionally stained yellow around anterior band. Plication plate generally similar in colour to parietal callus, often orangey in shells with white parietal callus. Small specimens often with purplish brown blotch on plication plate. Columellar lip profile somewhat sinuous, slightly concave posteriorly and convex around position of anterior band.

Agaronia gibbosa is variable in terms of shell morphology (shell shape, and spire height and profile), and to a lesser degree colouration. The shell is usually greyish to light brown, with an orange to cream fasciolar band patterned with dark blotches or flammules. Nevertheless all white 'albino' or orangey yellow 'golden' varieties are not very rare, and a few forms were named by Melvill (1904). The longstanding taxonomic confusion of Agaronia gibbosa (including nebulosa) with a few other species in the Sundaic region is perhaps due to uncertainty over the variability of this species and its distribution. Its distribution range is often mentioned to include parts of Southeast Asia and even the whole Indo-Pacific (e.g., Dance, 1990, 1992; Teso et al., 2011, Raven & Recourt, 2018), but there is thus far no reliable evidence of its presence beyond the Indian Ocean. This species appears to be a truly Indian Ocean species that occurs only at the very edges of the Sunda Shelf, along the western coast of Sumatra, Indonesia, and the western side of peninsular Thailand facing the Andaman Sea (e.g., Tantanasiriwong, 1978; Dharma, 2005). Specimens purportedly from Bali was figured by Voskuil (1990: pi. 4, fig. 3), but we have not been able to confirm the presence of this species in that area and consider the locality information to be erroneous. Other records in Sundaland are misidentifications of Agaronia adamii Terzer, 1992, and Agaronia Java new species (see also Remarks and chresonymies listed under those species). Notably Agaronia gibbosa is the only species with distinct blotches and flammules on its fasciolar band, which sets it apart from the others easily. Types of Voluta gibbosa Born, 1778 in the NHMW (NHMW 14208, NHMW 14209) are excellently figured in Teso & Pestorino (2011: 28, fig. 18).

Distribution. Widely distributed in the Indian Ocean, along the coasts of the Indian subcontinent, from the Arabian Sea, Laccadive Sea, Bay of Bengal to the Andaman Sea (e.g., Kirtisinghe, 1978; Abbott, 1991; Win & Swe, 2011).