Drillia pentagonalis Verco, 1896 Exomilus pentagonalis, common name the orange rib drillia, is a species of sea snail, a marine gastropod mollusk in the family Raphitomidae.

The spire is gradated, the whorls straight-sided in the anterior three-fourths, and bevelled at an angle of 45° to the posterior suture, which is distinct and simple.

The sculpture consists of five longitudinal ribs, continuous, narrow, erect and prominent.

The body whorl shows five longitudinal ribs, squarely rhomboidal, angulated near the suture, and carinated at the periphery, the ribs having projecting points here, and the carina being curved between them.

The margin is thin, simple, and sharp, straight for four-sevenths of its length, between the angle and the carina, curved towards the notch in the lower two-sevenths, and containing a well marked sinus in the upper seventh, rather more than a semi-circle, not quite reaching to the suture.