Bittium eschrichtii (Middendorf, 1849)

Common name(s):  Threaded bittium, Eschricht's bittium, Screw snail, Giant Pacific coast bittium, Threaded horn shell

Class Gastropoda
Order Mesogastropoda
Suborder Taenioglossa
Bittium eschrichtii, 8 mm long, found in a kelp holdfast on Shi Shi beach
(Photo by: Dave Cowles, Sept. 2007)
Description:   Members of Family Cerithiidae (horn snails) have a long spire with 8 or more whorls.  The aperture is much smaller than the length of the spire.  They have a short siphonal notch or canal, which is often at an angle to the long axis of the shell, but have no anal notch.  The shells have spiral ridges and sometimes have axial ribs which form beads where they intersect with the spiral ridges.  They are often found in shallow water, on grasses and seaweeds, in tropical and subtropical water. Bittium eschrichtii has no axial ribs, at least on the body whorl and the whorl next to it.  It has 9 or 10 whorls which taper to a sharp apex.  The whorls have prominent, usually flattened spiral ridges with grooves between.  The outer lip of the small, oval aperture is wavy because of the ridges and grooves.  The inner lip of the aperture is partially reflected into a very short and nearly indistinct siphonal canal which is angled toward the central axis of the shell.  Dull red to grayish brown or occasionally white.  Height to about 2.2 cm

How to Distinguish from Similar Species:   The other local members of Family Cerithiidae (all in Genus Bittium) have axial ribs and beads. Tachyrhynchus erosus does not have the tiny siphonal canal and is found in deeper water.  Batillaria attramentaria is black to tan with white flecks and bands, has a larger siphonal canal, and lives on mud in quiet bays.  Cerithidea californica, the California horn snail, lives farther south on mud in quiet bays, and has axial ribs and an expanded aperture.

Geographical Range:  Sitka, Alaska to Crescent City, CA [A more slender, spotted variety, B. eschrichtii montereyense, may be found from Crescent City, CA to Cabo San Lucas, Baja California]

Depth Range:  Intertidal to 55 m; mostly subtidal

Habitat:  Under rocks, in oyster beds, in sand or gravel, on coralline algae, on eelgrass

Biology/Natural History:  This is the most commonly found member of this family in this area and the largest Bittium species.  They feed on algae and detritus.  The empty shell is often occupied by small hermit crabs.  Predators include white-winged scoters.

Lays eggs from February to May.  There is no pelagic stage--juveniles emerge directly from the egg mass.



Dichotomous Keys:
  Flora and Fairbanks, 1966
  Griffith, 1967
  Kozloff 1987, 1996

General References:
  Harbo, 1997
  Johnson and Snook, 1955
  Kozloff, 1993
  Morris, 1966
  Morris et al., 1980
  Niesen, 1997
  O'Clair and O'Clair, 1998
  Rice, 1973

Scientific Articles:

Web sites:

General Notes and Observations:  Locations, abundances, unusual behaviors:

Authors and Editors of Page:
Dave Cowles (2007):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)