The shell reaches a maximum length of 80 mm and is fusiform. The spire is high, consisting of two bulbous nuclear whorls and eight weakly shouldered postnuclear whorls. The suture is in-distinct or weakly impressed. The body whorl is large and fusoid, and appears very large because of its broad varical flange. The aperture is of moderate size and ovate, with a barely perceptible anal sulcus. The outer apertural lip is erect and smooth marginally, except for three brief bumps reflecting spiral cords; its inner surface is smooth. The columellar lip is smooth and thickened, adherent at its upper end, detached and erect for its remaining length. The si phonal canal is sealed, moderately long, and almost straight.
The body whorl bears three winged varices. Intervarical axial sculpture consists of a single prominent node extending from the shoulder margin to shortly below it. Spiral sculpture consists of five major cords ending at the varical margin as partially open spines, and numerous fine threads, that are ephemeral between varices, becoming much stronger between and on the varical spines. The leading edge of the varix is richly laminate.
Shell color is uniform pale yellow-buff, in some instances with light-brown blotches.

Pterynotus swansoni: Shell trialate, yellowish-white; nuclear whorls more than 2, apparently smooth; postnuclear whorls 7, roundly shouldered; axial sculpture of 3 flattened, digitated varices between which are low, rounded knobs; spiral sculpture of a low rounded rib on the shoulder which is produced on the varices to long recurved digitations, slightly grooved on the face; on the base 2 similar, smaller spiral ribs are produced as shorter, recurved points; other spiral sculpture of fine striatums most prominent on the back of the varices, the front of the varices showing fine fimbriations; aperture ovate with a projecting margin, slightly raised at the junction with the 3 spiral cords but without dentation; canal closed for about two-thirds of its length, curved to the right; operculum thin, brown. The type measures: length, 59 mm.; maximum diameter, including the varices, 49 mm.

Pterynotus swansoni: Mexico. Gulf of California
Central Gulf of California (often trawled by shrimp fishermen docking at Guaymas, Mexico) to the Galapagos Islands.