^A. marina.^ Five to ten inches long; brownish-green; body cylindrical, thickest on the anterior end; anterior and posterior ends without chætæ; twelve to thirteen pairs of branched red gills on the central segments. It makes burrows eighteen to twenty-four inches deep on sandy southern shores, and can be traced by castings at the mouth of the burrow. Commonly known as "lugworm," and used by fishermen for bait.
In this family the gills arise from two semicircular bases forming the crown; the second lobe of the anterior extremity is reversed like a collar; the gill-filaments have secondary processes, and the tubes are flexible, composed of cemented mud or sand. Found under stones, the tube passing around the stone and opening upward.
^S. microphthalma.^ Length of tube one and a quarter inches, diameter one eighth of an inch; body olive-green, specked with white; wreath of tentacles half as long as the body; tentacles pale yellowish or flesh-colored, with transverse lines of darker color. It is found on the southern New England coast.
This family forms white calcareous tubes. One of the dorsal gill-filaments is flattened, forming an operculum, or cover, with [pg185] which the tube is closed when the worm has withdrawn itself inside. The tubes are commonly found attached to shells and rocks, usually solitary, but sometimes in clusters, crossing and recrossing each other on the surface of the shell or rock. Plume-like gills are attached to the anterior end of the body. The color differs in different species. These worms may easily be mistaken for the mollusks /Vermetus/, which live in similar tubes of larger size, growing in masses.
^S. dianthus.^ Tubes often three inches long and one eighth of an inch wide, the fixed end coiled and contorted, free end with circular opening; tubes often show circular ridges, marking periods of growth; operculum funnel-shaped, the exterior striated and the edge bordered with short processes; wreath of gills nearly circular and divided into two symmetrical parts; color variable. It is found in tide-pools, also on the under side of rocks at low-water mark, either solitary or congregated in masses, and ranges from Cape Cod to New Jersey.
^S. borealis.^ A minute calcareous tube, in a close, flat coil attached on one side; easily mistaken for a minute gasteropod shell; worm has an operculum and wreath of gills. Found on the fronds of seaweeds, on shells, etc.