Shell small to moderately small, ventricosely conical, with a low to moderate spire and a rounded shoulder. Outline of the last whorl rather convex. Concave spire, striated, with flat to slightly convex sutural ramps. Prominent protoconch measuring ca. 0.7 mm. The shell has a rich honey-brown color, with fine spiral lines of darker brown very often visible. The ground color is overlaid with irregular white markings, tent-shaped in many cases. The white marks are specially evident in a spiral band slightly below the midbody of the shell. The shoulder and the spire are patterned with irregular brown and white blotches. The aperture is white; but a purplish diffuse blotch is often present in the upper part, specially in the smaller specimens. Juveniles of this species are brightly colored and they can appear quite different to the adults. Their spire is clearly concave, with a projecting protoconch. The ground colour is greenish brown. There is one pale brown spiral band around the shoulder. The pattern of white markings is similar to that of the adult shells, but the tented aspect is more evident. The spire is also patterned with irregular blotches of white and greenish brown color. As the juveniles become mature individuals, the greenish shades disappear from the shell and the brown color becomes predominant. The aperture in these is dark brown, specially in the upper part. Morphometric parameters: L = 17-30 mm; average L = 23.4 mm; RD = 0.64 - 0.69; RSH = 0.08-0.16; PMD = 0.81 -0.84.

C. isabelarum n. sp. has been previously pictured in a number of works (Rockel. Rolan & Monteiro, 1980; Rolan, 1992 - population n°. 77; Monteiro, Tenorio & Poppe, 2004). It was initially considered conspecific with C. decoratus Rockel, Rolan & Monteiro, 1980 (PL 2, Fig. 5) from S. Vicente and Sta. Luzia Islands, and in fact shells of this species have been circulating as "C. cf. decoratus from Maio". However, the general aspect of the shell is rather different to that of typical C. decoratus, which has a characteristically angulated shoulder, a darker brown color, and usually a different arrangement of white markings in its pattern. The radular tooth of C isabelarum is narrower and has more denticles in the serration than C. decoratus. Egg capsules suppossedly from C. aff. decoratus from Pau Scco, Maio Is. (=C. isabelarum n. sp.) were examined by Rolan, 1992. Such capsules resulted quite different in aspect from those of C. decoratus from S. Vicente, and similar to those of C. verdensis Trovao, 1979 which has a very different shell and a different radular tooth. Based upon these observations, the fact that this population from Pau Seco was not conspecific with C. decoratus was already pointed out by Rolan, 1992, but the lack of sufficient live material for study prevented at the time its description as a distinct species.

TYPE LOCALITY: Baia de Pau Seco, West coast of Maio Island, Cape Verde Is.
Normally found around the type locality only, although there are reports of isolated specimens collected in Baia de Navio Quebrado.
Usually found at 2 - 4 m depth attached to the bottom of rocks and dead coral slabs on sandy bottom, or partially buried in sand under rocks.