The present species is characterized by 1) elongate-ovate, high-spired shell attaining 14 mm in height, 2) protoconch low-conical of 2.25 convex, smooth and glossy whorls, 3) spire straight-sided, somewhat stepped, made of gently convex whorls meeting at fine, adpressed sutures, 4) siphonal fasciole broad, with 6 flat, slightly imbricated spirals, 5) aperture small, with a narrow, deep and twisted abapical notch, 6) outer lip heavily swollen and ribbed within, 7) inner lip callused, with a parietal ridge and weak abapical folds, 8) sculpture of 13 angular ribs slightly nodulose at their adapical edge and of 2 spirals on lowermost base; surface otherwise smooth and shining; ribs reduced to adapical nodes toward the end of body whorl; color pattern consisting of brown adapical and abapical bands and of a distinct, reddish-brown peripheral line. Nassarius teretiusculus is readily distinguished from the most closely related species on account of the smooth shining surface devoid of spirals.
DISTRIBUTION AND HABITAT. Nassarius teretiusculus is an intertidal and subtidal element distributed from Indonesia to South China Sea. FOSSIL RECORDS. Pliocene of Indonesia.