In the Plymouth area Sabellaria spinulosa Leuckart is common on stones and shells below low tide mark in the Sound and on outside dredging and trawling grounds. It is often found on living Pecten maximus, much more rarely on Chlamys opercularis, and it is frequent on shells of Buccinum undatum, especially those inhabited by hermit crabs. Several tubes may be found close together, sometimes in contact, but it does not form massive colonies as it does on some shores bordering the North Sea and in deeper water of that region (McIntosh, 1922, pp. 14, 20). It is a smaller species than S. alveolata (L.) and its tubes, built mostly of mineral grains, are harder and stronger than those of the latter. At Plymouth the tubes attached to Pecten shells are usually larger, stronger, and include bigger grains, and are cleaner than are those on stones dredged in the Sound. Empty tubes are common, especially on stones and loose shells, and such tubes are sometimes tennanted by other worms.