The exhalant siphon of Xylophaga is greatly reduced and its opening is situated within the burrow. Faeces accumulate in the posterior end of the burrow in a compact mass.

The ctenidia and labial palps of Teredo, Bankia and Xylophaga are modified and reduced, unlike those of the Pholadidae. The ctenidia are flat and homorhabdic and possess no ciliary sorting mechanisms; they consist of the outer demibranch only.

The ctenidia of Xylophaga are composed of a direct lamella; those of Teredo and Bankia are divided into anterior and posterior portions connected by a branchial groove which is an extension of the marginal food groove of the gill. The number of filaments in the anterior portion of the gill varies according to the species, and is of assistance in identification.

The labial palps of Teredo norvegica are least reduced; in Xylophaga dorsalts reduction is greater, though selection of food material is still exercised. The greatest reduction has occurred in Teredo megotara and in T. navalis where there is no selection.

The ciliated mantle tracts in Teredo and in Xylophaga play an important part in limiting the quantity of food particles passed from the ctenidia to the mouth.