Shell medium-sized, attaining height of 16.7 mm, width of 16.4 mm, conical, nonumbilicate, coarsely sculptured. Protoconch 400-425 µm maximum diameter, 1 whorl. Teleoconch whorls about 7, flat; first 2 whorls with low, rounded axial riblets and 2 strong, beaded spiral cords; axial riblets gradually disappearing on whorls 3-5; spiral sculpture increasing by intercalation to 5-8 cords and 0-5 threads, of which abapical 2 cords forming periphery; periphery sharply carinate; adapical peripheral cord strong, projecting, set with strong, conical beads, beads crossed by 2 fine spiral threads producing squarish apices; abapical peripheral cord weaker, weakly beaded. Base weakly convex, with 13-17 narrow, weakly beaded spiral cords, adaxial 2-3 cords stronger, more widely spaced, and more distinctly beaded. Aperture subquadrate, lips thin, weakly crenulate; columella concave above, straight below, thickened, terminating in weak, rounded denticle. Shell ground color golden yellow with spots and axial streaks of brown; beads white; basal spiral cords with elongate spots of brown, darkest on adaxial 2-3 cords.

Shells of C. serratulum are most similar to those of C. rude but differ by having a much larger protoconch (400-425 µm vs. 350 µm), by being proportionately wider, and by having the adapical peripheral cord set with uniformly sized beads that are squarish in profile.

Type locality: Southwest of Cartagena, Colombia, JOHN ELLIOTT PILLSBURY Station P-375, 9°59.0'N, 76°02.0'W, in 135-130 m.
Distribution: Calliostoma serratulum is known only from empty shells trawled from off the northeastern coast of Colombia and northwestern coast of Venezuela in 119-187 m.