Vermetus maximus, Sowerby.
(Fig. 17).

Tryon, Man. Conch, viii., 1886, p. 184, pl. lv., figs. 89, 90; Morch, Proc. Zool. Soc. 1861, p. 166.

The Funafuti people consider this species good food, and call it " gea." It occurs in abundance in large clumps of Millepora growing on the lagoon side of the southern horn of the main islet. Here the earlier and irregularly coiled whorls were imbedded in the coral mass, but the last half foot of the tube stood up erect and free. What I consider the same species also grew, though rarely, on the outer reef-flat at low water, where it was altogether prostrate and had a more pronounced keel.

One fine specimen is thirty-five mm. across the aperture. Within the shell is white, smooth and porcellanous, at the slightly everted lip it has a faint purple tinge which soon fades. Externally it has a longitudinal, dorsal keel or crest, and is concentrically furrowed by growth lines. The distal part of the tube is, perhaps as a repair after injury, sometimes plugged with a shelly wad.

The animal is bold and active, if touched it shrinks two or three inches down the tube, but soon recovers confidence and rises to the aperture. The mantle margin is sometimes entire, sometimes notched dorsally. The long thick retractor or columella muscle is ventral.

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Beneath the head is a flap terminating anteriorly in two processes and arising from a deep cleft between the mouth and the operculum. Treating of the same or an allied species from Guam, Quoy and Gaimard^* describe this as an anti-buccal appendage and figure it from above. I regard it as the relic of a degenerated propodium. The accompanying sketch (.Fig. 17) in profile, of an animal half drawn out of the shell and stript of the operculum, will better convey an idea of this organ than figures taken from above.

When a gasteropod retreats into the shell it doubles the foot either lengthwise, as in some inoperculate forms, or across, as in most oper-culates. In the latter case when completely retracted, the foot is so folded head to tail that the anterior half of the sole is applied to the posterior; the operculum then closes the aperture. In a sedentary form this position of retraction might become permanent. Where the foot never serves for progression, but continues to maintain a useful operculum, it is easy to imagine that the fore part of the folded foot would become atrophied and that as it diminished the hind part would enlarge. This is the history suggested for the shrunken propodium of Vermetus, which lies tucked away between the mouth and the operculum. The process of evolution perhaps continued in the direction of utilising the appendices of the pro-podium as tentacles.

This species was collected by Hugh Cuming at Marutea, Pau-motus, and opercula of it were received from Lifu by Melvill and Standen. In a preceding article (p. 243) I have quoted a description of a mollusc from Mangaiia, called "ungakoa," which is probably this. In Java it is known as "karang," which Morch translates as "coral tube." The only Pacific shell with which this can be confused is the pipe-like Kuphus arenarius, L.