Shell size average for the genus. The shape is conical with slightly convex whorls. The body whorl takes almost 2/3 of the total shell height. Protoconch small and white. On the first whorl one spiral rib, on the second and third whorl the sculpture changes to become fully developed on the later whorls. Suture deep but easy to detect because of the convexity of the whorls. On the upper part of the body whorl there are about 5 primary spiral ribs covered with smooth knobs. The channel between these ribs is covered with a microsculpture of fine oblique axial striae. Each primary rib is bordered on each side with a fine tertiary spiral rib - hardly visible with the naked eye. The body whorl turns smoothly into the base which is covered with about 9 primary spiral ribs, linked together with axial striae. The interspaces between these ribs become smaller towards the umbilicus and the tertiary spiral ribs disappear. The umbilicus is small, narrow but deep. There are 4 teeth on the umbilical keel. The parietal callus is white and transluscent in the center. The columella is thick, white, double folded and bears a large bifurcate columellar tooth that protrudes into the aperture. On the umbilical side of the columella there are two slight elevations. About 7 labial plicae of varying strength inside the aperture. The color of the shell is constant: always a red-brown base color with lighter colored top whorls. The whole covered with dark brown dispersed and irregularly set spots that have a white shadow or that are entirely encircled by white. Occasionally these spots are set in rows together. In adults, there is occasionally a row of dark spots near the aperture.

We compare C. simoni n. sp. with its sister species C. margaritarius and the Japanese C. gemmulifer.
Clanculus margaritarius (Philippi, 1846)
Very simple characteristics distinguish this species at once. In C. margaritarius there is a developed blunt tooth near the parietal callus, inside the outer lip, hardly visible in C. simoni n. sp. The shell is higher, the knobs on the spiral ribs are bigger and the interspace between the spiral ribs is smaller. More olive colored than red-brown and the irregularly set blotches are more evenly spread.
Clanculus gemmulifer Pilsbry, 1901
Can be readily recognized by the broad shell, the much more raised spiral ribs, the more stepped whorls with a broad subsutural channel. The holotype of this species has no teeth on the columella or the columellar keel.

TYPE LOCALITY
The Philippines, Aliguay Island.

DISTRIBUTION AND HABITAT
Only known from the type locality, where it lives on sandy mud bottoms about 100 m deep.