Shell large, massive, robustly conic, earliest whorls mesocostate; subsequent whorls at first straight-sided, toward maturity strongly constricted mesially and developing a heavy pinched-out secondary carina at the lower quarter, below which the whorl is abruptly beveled into the narrowly channeled suture. General ornamentation composed of numerous narrow, close, flattish, spiral threads, one or two of which below the carina are cord-like. Growth lines with a single nearly meadian sinus or with weak sigmoid inflections toward the sutures. Base somewhat tumid at maturity, with 5 to 7 low heavy spiral cords. Aperture nearly circular in adult. Color of shell yellowish-ashen, heavily suffused and streaked with purplish-brown. Alt. of holotype 122 + , max diam. 30.4, alt. aperture 20.0 mm. Type Locality: The great mud-flat 8 to 12 mi. N. of San Felipe, Baja, California;

Comparisons: Probably the most imposing of living west American turritellids, this magnificent species has been confounded with C. goniostoma (Val.), from all forms of which it differs at maturity in the concave whorls, the secondary development of the strong beveled suprasutural carina, and some minor detailes of sculpture upon which reliance must principally be based in the more difficult separation of young shells.