The holotypc of Cerithium (Cerithiopsis) carinatum Smith is a straight and long shell with a broken protoconch and a fracture in the middle of its teleoconch. A clear definition of this taxon is necessary for comparison with other specimens; therefore, a redescription of the holotype is necessary:
Total length (without the lost first whorls of the protoconch): 5,8 mm; width of the last whorl: 1,5 mm. The teleoconch colour (possibly faded) is white, but with magnification, a light brown colour with white blotches can be observed. The protoconch is broken but the shell still has three complete smooth whorls which slowly decrease in width. It permits us to suppose that the complete shell could have had a spire of four whorls, or even more. At the end of the protoconch, the teleoconch begins with a cord in the middle of the whorl; the second cord appears above the first, and the third one in a subsutural position above the two first. The teleoconch, broken in the middle, has eleven spiral whorls. Each has three spiral cords of which the two upper ones are close to each other, while the third is a little distant from the second and is also more prominent; a fourth cord appears in the suture near the third whorl of the teleoconch and it increases a little on the last whorls but it never reaches the size of the first cord. On the last whorl are five cords; the fourth is at the level of the suture and the fifth a little below. A trace of a cord appears on the base of the siphonal canal. In the spaces between cords, there are axial striae, which are vertical between the second and third cords, and oblique, although in different orientation, between the first and the second ones and between the third and the fourth ones. The siphonal canal is short and open. Its extremity is at the same level as the last spiral whorl. The aperture is ovoid, a little rectangular and its free edge is sharp. This species is different from S. trilineata, which has a uniform coloration, is wider and has only three equal cords on each whorl, separated by equal spaces, and which has a protoconch with only two spiral whorls.