Biology/Natural History: This species was introduced from Asia, probably along with oysters. Since they seem to remain in areas near where oysters were planted, their larvae probably have a very short or no pelagic stage. This species is slowly replacing the native snail Cerithidea californica in California bays where they coexist. Both this species and C. californica frequently are infested with abundant cercariae larvae from flukes (Trematodes), and serve as alternate hosts to the flukes which infect seabirds.
This small snail has a tall, turretlike spire composed of 8 or more slightly rounded whorls and an acute apex. The aperture is rounded on the outer lip, which has teeth inside it. Its well-defined siphonal canal is less than 1/2 the height of the aperture and is twisted sharply toward the midline, almost at a 90 degree angle. The operculum is horny and multispiraled (see photo above). The outside of the shell has both axial ribs and spiral ridges, which tend to form larger "beads" where they intersect. Has about 12 axial ribs, which tend to fade out on the lower whorls, and 5-6 or more spiral ridges per whorl. The suture between whorls is not sharply impressed. Color grayish, with brown on the beads. A white band may be found below the sutures. Height up to 3 cm.
Geographical Range: Japan, other areas of Asia from 40 degrees N to south of the equator. Common in several bays in California and the Pacific Northwest where oysters have been grown, at least up into British Columbia.
How to Distinguish from Similar Species: There is only one (introduced) species from this family in this area, and this is the only locally common mudflat snail with a high, turreted shell. Among other turreted snails, this species can be distinguished from Cerithidea californica, the California horn snail, which lives farther south by the fact that the siphonal notch of C. californica is barely developed and does not twist sharply toward the midline (photo photo). C. californica also has a pallial eye on the edge of the siphon, which B. attramentaria does not have. Bittium spp. (Family Cerithiidae) also have a barely evident siphonal canal. They may have both spiral ridges and axial ribs, but the most common species, Bittium eschrichtii, has no axial ribs. Members of Family Cerethiopsidae ((e.g. Cerithiopsis spp.) have a siphonal canal which angles about 45 degrees toward the midline, may have well over 12 axial ribs, and rarely grow over 1 cm high. Exilioidea rectirostris (Family Neptuneidae) has a much more prominent siphonal canal (over 1/2 the height of the aperture) and prominent axial ribs but has only faint spiral ridges which do not form beads with the axial ribs.