Shell cylindrically ovate, of medium size to approximately 20 mm. Solid, spire very short, teleoconch consists of 4 to 5 slightly convex whorls, protoconch of two tiny mammillate, smooth glassy-white, embryonic whorls. The post embryonic whorl is encircled with 3 round, smooth, glassy white cords of equal size. The single spire whorl is encircled with 3 to 4 strong spiral cords separated by weakly punctate spiral grooves, cords are weakly bisected by axial grooves. Sutures are distinct. Body whorl sculptured with distinct, stair-step shaped spiral cords which number 23 to 25. The spiral cords are separated by deep, weakly punctate spiral grooves and are bisected by strong axial grooves giving the shell a distinctive nodulose appearance. Outer lip is thickened in adult specimens, finely crenulate. Columella with 8 to 9 white, round.
oblique folds. A white columellar callus extends the entire length of the aperture, being wider and thicker at the posterior end of the aperture. Aperture white and smooth within Shell white, straw-yellow, or tan in color. Intermittently circled with light tan lines or stains between the spiral cords, number of lines or stains varies from 0 to 7 on the body whorl. Some specimens appear to be spirally banded, alternately yellow and white. Some specimens are nearly solid tan in color. A few specimens have a few axial streaks of white which follow growth lines.

This new species is similar to Pterygia fenestrata glans (Reeve, 1844), but is smaller, not as elongate. lighter in color, orna-mented with much finer nodules. Pterygia fenestrata glans is sculptured with square, raised, stair-step shaped nodules. At the intersections of the spiral ridges and axial folds, the nodules are often tipped with a pair of white spots. This color pattern is not seen in the new species. Some authors (Cernohorsky, 199D consider Pterygia fenestrate glans to be a synonym of Pterygia fenestrata . Reportedly some Philippine specimens of P. fenestrata show intergrades of coloration, changing from the typical white shell of P. fenestrata (with its spiral decoration of lines of black periostracum) to the overall tan color of Pterygia fenestrate glans on the same shell. I have never observed such specimens in any museum or private collection. I have therefore retained Pterygia fenestrate glans as a valid subspecies pending discovery of an intergrade as mentioned above. This species is also related to Pterygia undulosa . Pterygia undulosa is found in the Red Sea and is generally larger than Pterygia undulosa ,reaching over 35 mm in size. Pterygia fenestrata glans rarely reaches 30 mm in size. Pterygia undulosa is very similar in color pattern to this new species, is more elongate, sculpture is larger, perhaps a little smoother. These three species. Pterygia fenestrata glans, Pterygia undulosa and P. purtymuni n.sp., all seem to represent species with a common ancestor. These species have also frequently been compared to Pterygia crenulata (Gmelin, 1791). Pterygia crenulata is also found in Hawaii. It differs from this new species, by being much larger, more elongate, sculptured with coarser nodules, of a different color pattern, being light tan with dark blotches and bands. The Hawaiian specimens are noted for having dark brown lines between the spiral cords and being quite elongate.

Type Locality
Maalaea Bay, Maui, Hawaii, 40 m.. dredged in pen shell beds.
Geographical distribution
Limited to the Hawaiian Islands.