The more noticeable differences of Alviniconcha compared with Provanna are:
—1. The size of the shell is much larger in Alviniconcha and the periostracum has strong bristles.
—2. The mid-oesophagus is thin and simple in Alviniconcha, not forming an oesophageal gland. This may be a reduction or simplification, due to reduced use or specialization of the alimentary canal.
—3. In Alviniconcha, the supraoesophageal ganglion is situated far behind the circumoesophageal complex. This may be related to the large size of the animal. In all molluscs the size of the components of the central nervous system increases less rapidly than body size and therefore the distances between the ganglia will become larger.
—4. Alviniconcha has no pallial tentacle.
—5. The suboesophageal ganglion of Provanna is farther separated from the left pleural ganglion than in Alviniconcha.
—6. Presence of a genital furrow on head-foot.
—7. Eusperm nuclei short and solid in Provanna, elongate and cylindrical in Alviniconcha (Healy in press).
From this we conclude that Alviniconcha belongs to the Provannidae and is modified in alimentary and circulatory characters by its symbiosis with sulphide oxidizing bacteria.