A snail that cements dead shells and stones onto its own as it grows.
A conical snail whose own shell is 3 to 10 cm across and is usually invisible under a load of cemented dead shells, coral fragments, pebbles and debris. The load is what is seen: on the sand a carrier shell reads as a small heap of rubble until it moves. There are about twenty species of Xenophora along with the related Onustus and Stellaria, and because they are separated on the shell underneath the attachments, a record from a dive is normally left at genus. The animals encountered on dived depths are shallow-water species; most of the family lives deeper than divers go, which is why the shells are better known from trawls than from the water.
The snail holds each object against the growing edge of its shell with the foot while the mantle cements it in place, so the load is a record of the ground the animal has crossed. Why it does this is not settled: camouflage, an increase in apparent size against predators, a prop that keeps the shell from sinking into soft sediment, and a cage that shelters the head while it feeds have all been argued. It feeds on detritus and small organisms taken from the sediment beneath the shell, which the raised attachments hold clear of the bottom.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.