Shell minute, elongate ovate, solid, spire rather short, light-brown ; whorls 6, spirally granulated, granules rather large, closely set, disposed in two rows on the whorls of the spire, the lower one the larger; base contracted, spirally ridged; aperture ovate, deep-brown, one-third the length of the shell; posterior sinus large, circular, margins nearly united; peristome rather sharp and Strongly arched; columella smooth, nearly vertical.
Length 2 mm.

Kay:
Shell: ovate; axial ribs cut into large nodules by spiral grooves; red-brown. Spire: protoconch of about four and one-half whorls, the apical one and one-half whorls smooth, the remaining whorls with a prominent, low-set carina; teleoconch of three whorls separated by a linear suture. Sculpture: convex, rounded, axial ribs cut by a deep spiral groove into two rows of nodules on each whorl. Aperture: narrowly ovate, about one-third the length of the spire; outer lip thickened; sinus subsutural, U-shaped, and with a large callus. Operculum: leaf-shaped with a terminal nucleus. Color: red brown. Anima!: exposed parts creamy white. Radula of simple marginals only (Powell, 1966)

Wiedrick, 2015:
Shell small to medium sized at maturity, shape ovate pupoid, narrow, color red-brown, occasionally with faint blotch on dorsal side of final whorl. Apex low profile, four protoconch whorls, first one to one-and-a-half whorls translucent white, small, compact round bulbous, proceeding three whorls red-brown with low carinate keel, finely beaded, upper section of final whorl with backward crescent shaped ribs. Three-and-a-half to four teleoconch whorls with two rows of tightly spaced, relatively close in sized nodules, sculpture somewhat clathrate, final whorl with very subtle ribs, beaded row at base, four cords on siphonal canal. Aperture very small, slender, ovate, about one fourth the height of shell, parietal callus very large, projecting outward, sinus extremely restricted, nearly sealed.

Length, 3 mm; diameter, 1 mm

Carinapex minutissima (Garrett, 1873) is characterized by its small size, on average, in comparison to its allied C. amirowlandae. Protoconch of C. minutissima with one-and-a-half translucent white whorls, proceeding whorls brown, profile low, proceeding three protoconch whorls with low carination, teleoconch whorls with two rows of tightly spaced rows of nodules, four spiral cords on final whorl of siphonal canal.

C. minutissima was described from Fiji. Also known from Hawaii and shells resembling those from Hawaii also occur in New Caledonia. This minute turrid is very common under rocks in tide pools and on fringing reefs, and occurs in sediments to depths of 60 m. New records show a wide distribution in the West-Pacific area.

The veligers are among the most abundant veligers in the plankton at Kaneohe Bay, Oahu; they metamorphose easily under culture conditions but do not grow much beyond their size at metamorphosis (length, 825 mu width, 560 mu) which suggests that they may be food specialists (J. B. Taylor, 1975). The premetamorphic protoconch has beaded spiral keels on the second, third, and fourth whorls and axial ribs on the third and fourth whorls (J. B. Taylor, 1975).