Diagnosis. According to Woodring (1928: 157), shell small, moderately slender; whorls moderately convex with a varix about ½-turn (“some distance”) from lip edge. Protoconch of 2 smooth whorls. Axial sculpture of narrow ribs that stretch from suture-to-suture, arcuate and reduced as “obscure prologations” in the sulcus, and spiral grooves and threads that may be reduced or obsolete on the axial ribs. Aperture long and narrow; outer lip with a relatively deep stromboid notch anteriorly and a deep U-shaped anal sinus posteriorly, near suture. Anterior canal moderately long, strongly constricted, deep, twisted to the right viewed ventrally and bent slightly dorsally, with an asymmetrical, deep notch at its tip. Inner lip detached; parietal wall with a heavy callus. Type species by original designation, Agladrillia callothyra Woodring, 1928, Miocene [now considered Pliocene (from Donovan, 1998)], Bowden, Jamaica.
Key characteristics. The combination of the following characteristics separate Agladrillia from other Drilliidae:
1. Shell sculpture of widely spaced narrow ribs that run from suture-to-suture, lower and recurved in sulcus, and of deep spiral grooves that are diminished or obsolete on rib crests;
2. Varix hump-like, positioned ½-turn from edge of outer lip;
3. Ribs obsolete on dorsum of last whorl, except in sulcus;
4. Anterior canal strongly constricted and deeply notched at its end;

Shell small to moderate, clavate-fusiform, base strongly constricted, with relatively long, slightly obliquely truncate siphonal canal, flaring sightly towards end; anal sinus deep, U-shaped, constricted by a moderate to large parietal pad, stromboid notch distinct; subsutural cord fairly strong (sometimes nodose) to absent; axial ribs strong, sometimes suture-to-suture, sometimes ending at shoulder, spiral sculpture variable; lip usually preceded by a varix. Protoconch of 2-3 smooth whorls. Radula drilliine, but lacking rachidians.

Two other genera also have deep spiral grooves. Calliclava McLean, 1971 differs in possessing a carinate, not smooth protoconch. Clathrodrillia Dall, 1918 has a smooth protoconch but differs in having a tapered rather than a “pinched” anterior canal, and a varix about ⅓-turn from the edge of the outer lip, not ½-turn as in Agladrillia.

The occurrence of this supposedly Western Hemisphere genus in southern Africa is open to confirmation. However, the two local species here described agree in principle shell characters with several West American species. Powell (1966) accepted only one Recent species (subsequently transferred by McLean (1971b) to Kylix Dall, 1919) as belonging to the genus, plus a second species referable to subgenus Eumetadrillia Woodring, 1928. McLean in Keen (1971) recognised five species from tropical West America. Eumetadrillia was proposed for species of Agladrillia in which the ribs stop at the shoulder and the subsutural cord and spiral sculpture are absent. These differences appear to be bridged in some of the eastern Pacific species treated by McLean. Radulae were figured by McLean (1971a) and described by Shimck & Kohn (1981).