Shell small (to 13.8 mm), broadly fusiform, thin, glossy, translucent between axial ribs; of about 8-8,5 strongly convex whorls, suture impressed, undulant above axial ribs of previous whorl; last whorl approximately 61% of total length. Protoconch of approximately 1,75-2 smooth round whorls. Axial sculpture of narrow but strong sigmoid ribs about twice their width apart that run from suture-to-suture on spire whorls and evanesce on shell base below periphery; ribs narrower on shoulder with crests almost wing-like; crests lower, broader below whorl periphery; 8-9 on the penultimate and 6-9 on the last whorl to the varix. Faint growth striae over entire shell, strongest on last whorl. Spiral sculpture of 4-5 threads on shell base that are strongest anteriorly and 5-6 threads on anterior fasciole. Sulcus absent; former positions of the sinus marked by recurved ribs on shoulder. Varix cup-handle-like behind anal sinus. Anal sinus on whorl shoulder, U-shaped, deep, inner edge of sinus flared out. Outer lip thin; edge of lip from and congruent with anal sinus traces a broad arc to the stromboid notch. Anterior canal short but well-defined, open, tip turned to the left when viewed ventrally; canal end unnotched; anterior fasciole not swollen. Inner lip narrow, emarginated, thick on anterior canal, thinner in parietal area, and forming a parietal callus posteriorly. Color white with a light golden brown band just below whorl periphery that is visible on spire whorls above suture.

Cerodrillia occidua has all the key characteristics of Cerodrillia—a glossy shell devoid of microsculpture except for spiral threads and ridges on the shell base and anterior fasciole, a cup-handle-like varix behind the anal sinus, and axial ribs that extend from suture-to-suture, without a sulcus. Variability. The 11 measured specimens have an average total length of 11.20 mm (8.7-13.8 mm) and average W/L ratio of 0.433. Identification. Cerodrillia occidua possesses sigmoid ribs very much like Douglassia bealiana Schwengel & McGinty, 1942 but differs in being larger (average 11.22 versus 6.83 mm), a lighter color, and with a color band broader, more diffuse, without the additional white band. It has bulging whorls like C girardi Lyons, 1972 but differs in having a taller spire (average W/L ratio = 0.433 versus 0.480), a less globose body whorl, lighter color, and in possessing a color band that is lacking in C girardi.

Campeche Bank, Mexico. Reported in mud at 63-65 m depths, and also noted as "common" on the sample label.