Shell large, robust, 50 - 70 mm., biconic-fusiform, with a tall turreted spire and a moderately long, straight to slightly recurved anterior canal. Resembling Clavatula in the coarseness of the sculpture and especially in the moderately high clasping adpressed suture, but the operculum is leaf-shaped with a terminal nucleus, not clavatulid, that is with the nucleus medio-lateral. Adult sculpture of broadly rounded to angular prominent axials overridden by coarse spiral cords. Typically the shell is covered by a thick periostracum. Sinus deep, U-shaped, occupying the middle of the shoulder slope .Radula with a minute unicuspid vestigial central tooth and a pair of modified "wishbone-type" marginals, in which the distal limb of the base is severed from the rest of the tooth. Knefastia resembles Clavatula in its adpressed suture but lacks the heavy nodose subsutural fold of that genus. Also the operculum is more in accord with that of the turriculid genus Comitas. Range — Recent, Gulf of California to Ecuador. Miocene to Oligocene, Washington, Costa Rica, Panama, West Colombia, Peru, Florida and Dominican Republic. (Also recorded from the Miocene of France and Angola, and the Pliocene of Italy, but these claims require substantiation).