Shell highly turreted, large, up to 12 whorls, sculptured by regularly spaced axial ribs throughout, only exceptionally these ribs may lack completely; in some specimens, ribs support a spiral row of spiny nodules.
Description
Shell: Medium sized to large, solid but not very thick, 6 to 12 whorls, pyramidal spire, frequently eroded tip; colour uniform light to olive-brown; whorls well rounded in diameter, separated by well-defined, thin suture; sculpture of basal spiral ridges and regularly spaced axial ribs that occasionally support small, spiny nodules arranged in a spiral band at centre of whorl; some specimens smooth; aperture wide, well rounded at base, comprising about 1/5 of shell height. Size: H = 20-87 mm, B = 8-36 mm.
Embryonic Shell: Smooth except for fine growth lines. Maximum height 4 mm, 3.5 whorls. Average proportions: H = 2.3 mm, B = 1.1 mm, HA = 0.27 mm, BA = 0.48 mm, DA = 0.63 mm (for n = 6).
Operculum: Slightly oval, four to six whorls, central nucleus; almost fits aperture.
External Morphology: Uniformly coloured, dark grey to black; grey foot sole with scattered light spots.
Radula: Ribbon length of up to 30 mm, corresponding to about half of the shell height, about 180 rows of teeth. Rachidian with single main cusp, three smaller denticles on each side tapering in size; upper margin concave by inflated, rounded corners; lower rim rounded; glabella narrow, well rounded at its base, lateral margins slightly concave. Laterals with main cusp flanked by three smaller denticles. Inner and outer marginals with two to three denticles, somewhat pointed, of about same size and shape.

Reports from Sri Lanka (Annandale, 1920), Hainan and China (Yen, 1939), Sumatra and Java (Rensch, 1934; Benthem Jutting, 1956), Thailand, the Mekong, Borneo (Brandt, 1974), Melanesia (Abbott, 1948), and the Philippines (Bandel & Riedel, 1998) refer to other species.
Conchologically similar are B. episcopalis from the Malay Peninsula, B. sumatrensis from Sumatra, B. herculea from Myanmar, and BJullienifrom Cambodia; all were repeatedly synonymized with B. costula. Brotia episcopalis and B. sumatrensis tend to be smaller and more conical in shape. In B. episcopalis, the upper whorls are smooth and axial ribs are more conspicuous and not as regularly spaced as in B. costula, in which closely spaced axial ribs are always present. BJullieni exhibits a larger, broader, and more conical shell, with a more pronounced spiral sculpture .
Adamietta species formerly assigned to B. costula, such as A. infracostata (Mousson, 1849), differ in embryonic shell morphology (Kohler & Glaubrecht, 2001, for the "Brotia testudinaria-group").

Distribution
Northeast India (Bihar, Uttar Pradesh, Madhya Pradesh, Manipur, Meghalaya, Mizoram, Sikkim, Assam, West-Bengal), Bangladesh, Bhutan, and Nepal. Namely, Ganges-Meghna-Brahmaputra River system with affluent rivers.

Habitats
Clear creeks with sandy bottoms, large riv¬ers, and even ponds (Subba Rao, 1989).