The shell is small (maximum length 25 mm) and roughly fusiform. The spire is high and acute, consisting of one full nuclear whorl and six strongly shouldered, excavated postnuclear whorls. The suture is weakly impressed. The body whorl is large and fusoicl. The aperture is suhcircular to ovate, with a barely discernible anal sulcus. The outer apertural lip is weakly erect and broadly crenulate; its inner surface is smooth. The columellar lip is also entirely smooth. The siphonal canal is moderate in length, with fused margins.
The body whorl bears three briefly spinose varices. Intervarical axial sculpture consists of a single knob, closer to the older of any two consecutive varices. Spiral sculpture consists of a weak cord at the shoulder margin and seven obsolete cords below it, the last two on the canal. Where the cords intersect the varices, short, sharp, curved, ventrally fused spines are developed. The spine at the shoulder margin is much the longest, hooking sharply posteriorly to touch the preceding whorl. Of the remaining six vcntrally curving spines, three arise on the lower body and three on the canal. The entire shell surface is covered with minute, oblique "chisel-holes."
Shell color varies from cream and pale orange-pink to dark purple-brown.

Numerous authors have suggested that this species is conspecific with Poropteron uncinarius. The differences are as follows:
P. uncinarius
1. Shoulder spine hooked posteriorly and bent dorsallv
2. Shoulder spine not touching previous whorl
3. Varix bears five straight or dorsallv bent spines
4. Shoulder region sloping and unexcavated
5. Occurs subtidally
P. incurvispina
1. Shoulder spine hooked posteriorly, dorsal curvature lacking
2. Shoulder spine bent posteriorly, touching previous whorl
3. Varix bears seven spines, the lower six vcntrally curved
4. Shoulder region sharply angular, excavated
5. Occurs intertidally