Shell oval-lenticular, white, fragile and not translucent, with depressed apex. Protoconch only 1 whorl. The nucleus has a diameter of about 0.100 mm, sculptured from the beginning with 6 spiral undulating cords; subsequently the lower one or two cords are immersed in the suture, with only four visible at the end. In the interspaces there are many fine microscopic axial lines, which originate obliquely from these cords. The colour of the protoconch is white. Teleoconch with about 1,5 whorls, with a fairly rapid development. It is sculptured with fine prominent axial ribs, which are slightly curved; they number only about 12 on the first half whorl, but later they are closer and can reach 60 or more on the last whorl. Many fine spiral striae cover the shell and are evident in the interspaces, crossing the ribs to make them appear granular. Aperture ovoid, with the outer lip sharp, only contacting the penultimate whorl for a short distance. Previous whorls and the ends of the crowded axial ribs are visible in the open umbilicus, which lacks a peripheral keel. Dimensions: From 1.40 to 1.70 mm.
Radula with a rachidean tooth which has 1-2 small denticles on the base of the basal supports, a triangular sharp area with a prominent central cusp, and 5-6 smaller on each side. Lateral teeth very wide, with a gross and blunt denticle in the middle of its sharp area, 12 more on its external margin and 5-6 on the internal one. Marginal internal teeth narrower and longer than the lateral ones, strongly curved in the upper third, with numerous denticles (30-32) on their margin. Marginal external teeth oar-shaped, strongly curved and pointed, with the external margin smooth and denticles on the internal one.

The shell of M. worsfoldi can be differentiated from M. robertsoni, M. garcesi, M. palmalitoris and M. paradoxa by its not very prominent protoconch. The most similar shell is that of M. canarreos , but the latest species has the interval between the cords of the protoconch smooth and not with microscopic lines; also, it has 7 spiral cords, instead the 5-6 of M. worsfoldi (only 4-5 visible at the end of the protoconch). The teleoconch of M. canarreos has more ribs, and they are also more attenuated. The species of Megalomphalus have a different teleoconch and protoconch.