Left, an interesting photograph shows the underside of a carrier shell, with the mollusc in process of cementing an empty shell from the ocean floor to its own shell. The very long proboscis, characteristic of the Xenophoridae, is extended vertically with a foreign shell attached to its tip. 

Right, a similar carrier shell shows numerous small shells cemented in place around the edges of each whorl. In older specimens the main shell may be nearly obscured by these attachments