Olivellites, a Pennsylvanian Snail Burrow

Abstract

While examining trails, burrows and cemented tubes in Elkhorn Slough, a tributary of Monterey Bay, California,t we found numerous individuals of the snail, Olivella biplicata Sowerby, feeding beneath the sand. In so doing they left contorted, gently convex elevations with a sharp ridge down the center and indistinct transverse wrinkles. The convex elevation was produced by the shell as a whole; the central ridge by the long siphon, which extended upward to the water. The transverse wrinkles, which were concave forward, appeared to result from side-to-side movement of the shell. The point could not be determined by digging, since water obscured all marks if the loose sand was disturbed, but it appeared that these wrinkles must be represented by a series of irregular vertical layers in the sediment pushed behind the moving snail. The whole structure resembled the Spongeliomorph, Cylindrites, discussed by Rieth,2 or the reverse of Cruziana casts recently illustrated by Hadding.3.