Nucleus smooth, milk-white, polished, bulimoid, two-whorled; when the irregular growth commences the nucleus may be turned upside down or take almost any other position, most appear to lie on their sides. Early part of the shell prone, irregularly contorted; as the whorls lie, the normal sculpture appears to be a single minutely undulated longitudinal ridge on the middle of the back with a space either side, then four or five similar ridges, parallel, close-set, and becoming obsolete as the tube begins to be erect. Between the longitudinal ridges are, in fine specimens, fine elevated transverse line. The sculpture is very variable in strength and often more or less obsolete. When the tube begins to rise vertically it loses all its sculpture except irregular incremental lines, and its calibre perceptibly diminishes. The color is yellowish or grayish white. The height of the erect part is usually about an inch, and the diameter of the aperture 1.75 mm. The greatest diameter of the same tube (distortions apart) would be about 2.0 mm.
Internally, very near the apex, are two laminae. The right one is large, arched over with a thickened edge, the left one lower, thinner, and overshadowed by the other. Both are subtransparent, with opaque whitish streaks. These laminae are however very irregular; they seem to be altogether absent in some individuals, and are perhaps sexual. They are obsolete or nearly so in most specimens, and I have had to break many before finding a single perfect example of these appendages. The animal is soft and whitish. I could see no eyes or tentacles. The operculum was translucent, spiral, as large as the aperture, with a smooth flexible edge, the outside concave and polished. Owing to the fact that the last whorl of the operculum seems to cover up the others with its inner edge except toward the centre, it is difficult to ascertain the number of turns. Very few of the numerous specimens contained the animals, many were occupied by parasitic sipunculoids, cheetopods of several species, and even Crustacea.

Nucleus small, polished; early part of shell prone, irregularly contorted; longitudinally ridged and in fine specimens decussated; latter part of the tube rises vertically or nearly so, is smaller and nearly smooth. Color yellowish or grayish white. There are two internal laminae near the apex.
Height of erect part, about 25; diameter of aperture, 2 mm.

Petaloconchus erectus (Dall, 1888) Erect Wormsnail
Distribution: Texas, Florida to Brazil; Bermuda. Size: Length 25 to 40 mm .
Description: Color white; shape circular, irregular tube at base and uncoiling to almost straight toward aperture; present as colonies as well as individuals, colonies may have several tubes sticking out from one group, individuals will be coiled at the base and straighten out and up; sculpture having the appearance of being smoothed out by a hammer. Habitat: Commonly found in large aggregates on rocks, shells, and/or other hard substrates. Depth range 2 to 1400 m (7 to 4592 ft).
Remarks: Shell is coiled at base for several whorls, then straightens out, and grows upward for approximately 25 mm (1 in). See Warmke and Abbott (1961); Vokes and Vokes (1983).

Caribic.