Shell height ranges from relatively low to medium pro-files. Shell ribbing typically consists of irregular ribs, and shells less than 10 mm in length tend to be smoother, but still have a knobby texture. The aperture and growth lines are irregular. The apical area erodes to white and the initial shell is dark with approximately six to eight white rays radiating from the apex. Subsequent shell color varies from predominately black with radially drawn out white markings or predominately white with black radial markings corresponding to coarse irregular ribs In most cases, the markings on both the white and black ground colors do not extend from the apex to the margin, but rather stop and restart in different positions. In the lighter shells the white areas are marked with brown markings; in darker specimens the brown markings are more sparse, but are often visible at the margins associated with the white markings. Occasional small specimens (less than 10 mm in length) are found that are completely brown in color . The ribs are not regular but instead often form knuckles or knobs at irregular intervals from the apex to the margin, and do not protrude to form a crenulated margin; in smaller specimens the shells are typically smoother.
The inner surface of the shell is typically marked with a brown or yellow-brown apical stain that clearly delineates the interior boundary of the shell attachment muscle scar. Sporadic darker markings may also be present in the central area. The intermediate area ranges from blue to white and is often overlain by a yellow-brown stain as well. The interior margin is broad and dark, reflecting the outer white markings. In the small brown shells the entire interior surface is brown with the central area being slightly darker than the intermediate area and margin. The edge of the aperture is slightly reflected back.
Radula : The first lateral teeth have sharply pointed cusps that flare out laterally. The second lateral teeth are also pointed, the inner tooth margins are concaved, and the outer margins slightly convexed. The cusps lie close to the edge of the radular ribbon. The third lateral teeth are reduced and also sharply pointed. They lie lateral and almost perpendicular to the bases of the second lateral teeth. The third lateral teeth are distinct from the second lateral teeth except at their bases. The third lateral cusps extend posterior to a position similar to that of the second lateral cusps. The uncini on the radular membrane are prominent and appear rounded.
Holotype dimensions: Length 20 mm. width 16.5 mm, height 4.2 mm.

Type locality (Figure 1): MEXICO: Baja California Sur; Bah fa de San Francisquito [Holotype]. MEXICO; Baja California Sur: La Paz and Tecolate [Paratypesl.
Type material: Holotype UCMP No. 157007, Paratypes UCMP Nos. 157003, 157006-157008. Paratypes have also been deposited in LACM and USNM.
Distribution: MEXICO: Baja California Sur; Bahfa de San Francisquito (28°30'N, 112°40'W) to La Paz (24°10\ 110°21') and MEXICO: Sonora; Guaymas (27°56\ 110°54').