Shell small, thin, compressed, moderately oblique; hinge long; ears large, the anterior slightly the wader and ornamented by 7 to 9 finely lamellose radial threads; notch deep, subacute; ctenolium septemdentate, posterior ear weakly furrowed, the ribs nearly obsolete. Right valve with 17 to 19 low, rather broad, gently rounded radial ribs set off by incised lines; alternate ribs on the older portion of the shell a little stronger and the 2 or 3 posterior ribs yet more emphasized; toward the antero-dorsal angle 3 or 4 ribs are narrower and bear a delicately beaded keel on their ridges. Left valve a trifle more convex, but similarly sculptured except that about every third rib is a trifle stronger than the others. Color either Acajou Red with a little dim speckling, or clear Apricot Yellow, the right valve always a trifle the lighter. Max. long, of holotype 7.4, alt. 7.1, max. diam. 2.0 mm. Type-Locality: 6-10 fms., off Acapulco, Mexico.
Comparisons: This is a tiny but gay little scallop which differs strongly from the associated P. velero Hertlein in the width and flatness of the ribs, as well as in the lack of cross-lamellation on the disk, and the lively coloring.