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A "mystery" piece of tissue was collected in the same trawl with this worm, which may very well be its proboscis, though the anterior end showed no obvious scar where the proboscis may have detached. The tissue was about 3 cm long and slightly smaller diameter than the worm. It was curled into a trough shape on one end and appeared nearly cylindrical on the other end. It had a velvety, dark red interior and an orange-red exterior, somewhat more orange-red than the animal's body.
The following description of burrowing in a related Echiuran (Echiurus pallassii, an east coast species) is by C. B. Wilson, excerpted from Johnson and Snook, 1955: "The animal rests upon its ventral surface, thus bringing its two large anterior setae in contact with the mud. The proboscis is turned upward and backward and remains thus with its edges somewhat rolled in and takes no part in the burrowing. The anterior end of the body is made wedge shaped, the under surface flattened and extending forward with the two setae projecting from its anterior edge. These are thrust into the mud and then the hinder part of the body is drawn forward. This is anchored by the anal bristles and the anterior end is pushed still further down into the mud. The process is described as being very slow, taking 40 minutes to get the body out of sight below the surface. The burrow goes down diagonally 10-18 inches, then horizontally 6 inches to 2 or 3 feet and then vertically to the surface. Once at the surface, the anterior end comes out far enough to free the proboscis and get it in its normal position, and then the body is withdrawn. Mud washes into the unoccupoed parts of the burrow, but an opening the size of a lead pencil remains, through which the proboscis is thrust in search of food when the tide is in. The proboscis may extend to a length of 5 or 6 inches. When a piece of food is located, the proboscis rolls to form a tube, and the inner surface being ciliated, a current is produced which carries the food into the mouth."