DIAGNOSIS. Shell: Spire moderately tall; sutures channelled, with flat-sided to lightly convex whorls and finely to rather coarsely gemmate sculpture. Peripheral angulation sharp on spire, where it is near base of whorls; last whorl sometimes rounded. Body whorl with 4-7 spiral rows of rounded to weakly scaled gemmae below suture, uppermost slightly stronger than others; peripheral sculpture subspinose to spinose, 20-30 spines when present; spines short, hollow, triangular. 1-3 rows of gemmae below peripheral angle and a third, heavier row of smooth or weakly scabrous nodules on rather weak basal angulation. About 4-8 rows of smallergemmaeon base. Entire surface crossed by prosocline axial lamellae, sometimes very distinct. Basal callus moderately expanded, thin , transparent, whitish, separated from white columella by a groove. Outer lip slightly reflected above. Surface pale fawn to pinkish-mauve sometimes with darker mauve blotches.
Operculum: Nearly circular, thickly convex, with faint, closely spaced spiral grooves around the margin; central area somewhat flattened with a few indistinct wrinkles, white.
DIMENSIONS. A. bathyraphe, holotype: height 34 mm, diameter, 33.7 mm. A. gilchristi, holotype: height 26.9 mm, diameter (including spines) 29.4 mm. Squamose specimens from Maldive Ids, 229 m: height 38.6 mm, diameter 35.7 mm; height 35.8 mm, diameter 31.7 mm.
TYPE LOCALITIES. A. bathyraphe: N. Maldive Atoll, N. Indian Ocean, 384 m ("Investigator" Stn 218). A. gilchristi: Bearing N.W. Y4 W, 15 km from O'Neil Peak, Natal, 165 m.
OTHER LOCALITIES. South Africa: Scottsburg Lighthouse, Natal, bearing N.W. by N., distant 12.8 km, 168 m; off Port Shepstone, 457 m; off Cape Natal, 99 m; off Cape Vidal, 146-183 m; off Durnford Point, 165 m; all from Barnard (1963, p. 221).
An examination of the small amount of material available to the writers has indicated that one rather variable subspecies of theguttata group can be recognized in the western and northern Indian Ocean. Specimens from S. W. Malagasy Republic and S.E. Africa (including the type of Astralium gilchristi) are similar in having a distinctly spinose periphery, flat whorls, and a colour pattern of dark blotches. Of the two lots available from N. W. Malagasy Republic, one is like gilchristi and the other 5 specimens from deeper water are more heavily beaded, non-spinose, have a uniform colour pattern, develop weak spiral striae over the closely packed gemmae and have a yellowish edge to the basal callus. These latter specimens are somewhat similar to the type of B. guttata bathyraphis from the Maldive Islands in general form but that specimen is a little larger, has stronger gemmae and lacks the secondary spiral striae and yellow-edged callus. In most respects the holotype of bathyraphis shows intermediate shell characters between gilchristi and the non-spinose shells from N.W. Malagasy Republic. A lot of 3 specimens, also from the Maldive Islands, have weakly convex whorls and distinctly scaly sculpture. A single specimen from the Bay of Bengal has a weak subsutural channel and is, in this respect, and in having a lightly convex shoulder on the body whorl, similar to 6. guttata millegranosa. It is, however, like B. guttata bathyraphis in other characters.
Finlay (1926, p. 367) commented that B. guttata bathyraphis is similar to "Incilaster" marshalli (Thomson) but the similarity of B. guttata bathyraphis is much greater to B. flindersi flindersi (T. Woods) and the Italian Pliocene B. castrocarensis (Forest!) (Sacco 1896, pl. 1, fig. 39, 40), although B. flindersi is much smaller and not closely related. B. guttata bathyraphis has fewer rows of more rounded nodules, a more clearly differentiated row of peripheral nodules, a more marked sutural channel and a more marked basal angulation than those of B. flindersi. Bolma castrocarensis does not have differentiated peripheral nodules and has more convex whorls than B. guttata bathyraphis, its sculpture consisting of seven or eight lateral rows of large, rounded, slightly laterally compressed nodules and five or six basal rows of slightly smaller nodules. The basal callus is broad and thick in B. castrocarensis, but narrow in B. guttata bathyraphis, and the two forms are probably not closely related.