The shell is large for the genus (maximum length 45 mm) and fusiform. The spire is high, consisting of one and one-half nuclear whorls and five barely shouldered to convex postnuclear whorls. The suture is weakly impressed. The body whorl is of moderate size and fusoid. The aperture is moderately large, with a narrow, shallow anal sulcus angled toward the left. The outer apertural lip is unthickened and barely crenulate; its inner surface is moderately strongly lirate. The columellar lip is entirely adherent and smooth, except for a barely discernible swelling at its anterior end. The siphonal canal is moderately short, straight, narrowly open to the extreme right, and barely recurved at its distal end. The body whorl bears eight to 12 axial ridges, ranging, even on a single whorl, from strongly prominent to completely obsolete. No true varices are present. Spiral sculpture consists of seven weak major cords, one on the shoulder and six on the body; between consecutive major cords there is generally a single minor cord, and the canal bears four to six minor cords. The intersection of the spiral cords and axial ridges is marked by the development of weak nodules.
Shell color is yellow-gray to blue-gray, becoming brown where worn. The aperture is pale fleshy yellow; within the aperture three transverse bands of brown-purple overlay the yellow color.

Shell. Solid and opaque, not glossy. A tall, conical and sharply-pointed shell, its apical angle about 54°, the spire often a little cyrtoconoid in profile. There are 7 - 8 tumid whorls which meet at sutures placed below the periphery of the upper whorl and made sinuous by the apical ends of the ribs. The ornament consists of spiral ridges and grooves, growth lines, and costae. The spiral ridges are numerous, distinct, low, and undulate in transverse section, approximately equal in breadth to the intervening grooves. Smaller ridges often lie along the larger grooves. The ridges are variable in number but there are usually 16-18 more prominent ones on the last whorl, 9 - 10 on the penult, 7 -8 on the antepenult, falling off slightly irregularly to 2 - 3 on the oldest whorl of the adult shell. They are sometimes poorly developed on the subsutural area of each whorl, especially the last whorl. There is no marked keel over the siphonal canal as in Nucella. The costae are prominent, broader than the grooves between, with rounded summits. Though predominantly prosocline they can vary considerably in direction on one and the same shell and from whorl to whorl, especially towards the apex. They may become orthocline or even opisthocline. Their number is also variable, 10-12 per whorl. They cross the whorls of the spire from suture to suture but die out on the last whorl about half way between the periphery and the base. Spiral ridges and growth lines are usually eroded from the summit of the costae.
The protoconch is small, about 100 um in diameter, has 1.25 whorls, and is smooth.
Aperture. An elongated oval, its long axis lying at about 20° to that of the spire, surrounded by a peristome and extended basally into a siphonal canal. It lies in a slightly prosocline plane. The outer lip arises from the last whorl nearly tangentially just below the periphery. Its initial section is rather straight, corresponding to the subsutural area with reduced spiral ridging. It then curves, somewhat abruptly in many shells, towards the base and this peripheral region may be a little flattened. At the base it turns to form the outer edge of a short, nearly straight and widely-open siphonal canal which continues the direction of the axis of the aperture, its tip turned back a little from the apertural plane. The columellar region is nearly straight, broad but not hollowed, with the lip curving outwards so as to obliterate all trace of umbilical groove. The inner lip forms a rather broad glaze over the last whorl, obscuring all the ornament. The edge of the outer lip is thin in young shells; in mature ones it thickens somewhat and there may be a ridge-like thickening a little way up the throat. The inner edge of this lip is ridged by the spiral ornament and on older shells there may be up to 6 more prominent ridges. The throat is extremely glossy.
Size. Up to 40 X 20 mm, but usually about half that. Last whorl = 64 - 74% of total shell height; aperture = 45 - 50% of total shell height. Females are larger than males.
Colour. Yellowish or dirty grey-white. The costae arc often paler than the grooves between and there may be irregular brown marks. The throat is brown or lilac-grey, paler just within the outer lip and at the base of the columella.
Animal. The head is small and flattened, not extended into a snout, and bears two tentacles; their bases are close together and they diverge markedly. Each is dorsoventrally flattened and bears an eye about one third to one quarter of its total length behind the tip, the section distal to the eye more slender than the base. The mouth (= opening of a proboscis pouch) lies on the underside of the head. The mantle edge is a little thickened, but smooth, and is extended into a siphon on the left which hardly projects from the siphonal canal. In males a sickle-shaped penis arises from the floor of the mantle cavity a little behind the base of the right tentacle.
The foot is small, truncated anteriorly, slightly embayed in the mid-line and drawn out anterolateral^, broadly rounded behind. Its anterior edge is double, carrying the opening of an anterior pedal gland, and a rather depressed area bordered by a low ridge on each side runs over the dorsal surface of the propodium from the mid-point to the level of the mouth. The sole is marked by two openings in females, one in males, both in the mid-line in the anterior half of the foot. The opening common to both sexes is that of the accessory boring organ (ABO), a cylindrical structure with slightly expanded end. housed in a sac which opens inconspicuously to an oval depression. The opening found only in females is that of the ventral pedal gland. The operculum is oval with lateral nucleus.
Colour. Cream-white with some dark markings on the tentacles and mantle edge.
Geographical distribution. This animal is primarily a native of the eastern American coast between Prince Edward Island and the northern parts of Florida. It has, however, been accidentally transported with oysters to various other places and has colonized some of them. In N. America it is now found on the west coast between British Columbia and San Francisco. In Britain it occurs in Essex (estuaries of the rivers Colne, Blackwater and Crouch and on open coast roughly between Clacton and Frinton) and in Kent (off the east end of Sheppey, the entrance to the Swale and east as far as Heme Bay). Although U. cinerea may well have been imported to other oyster-growing areas it has not apparently persisted in them.
Habitat. On the lower half of the beach to depths of c. 12 m in Britain but to about three times that in America. The bulk of the population is sublittoral. It is always associated with oysters and so likes stony or shelly bottoms, avoiding mud. When the temperature falls to 7°C or less the tingles hibernate, burying themselves in soft parts of the substratum. They are sensitive to reduced salinity in summer and die if it falls to c. I7%o or less. At winter temperatures they are much less affected and can apparently then survive for long periods at salinities down to 8%°.

The eastern coast of North America from Prince Edward Island to the central portion of the eastern coast of Florida. Reports of this species from the western coast of Florida have never been verified. A giant form is found on the outer coast of Virginia (e.g. Wachapreague, Va.). U. cinerea has also been introduced with oysters into several localities on the west coast of the United States, particularly in the San Francisco Bay area; although these populations are apparently self-sustaining, little range expansion has been reported.

Distribution: Florida, Texas.
Size: 51 mm.
Specimen in photograph a subadult, 17 mm high. Description: Color tannish-yellow; shape fusiform; sculpture of 9 to 11 rounded axial cords and numerous spiral threads; aperture ovate; siphonal canal short. Habitat: Shallow water; on oyster reefs at depths from 0 to 18 m (60 ft). Remarks: First record from Texas and Gulf of Mexico, collected at SPI (1969). One of the major predators of oysters in the western Atlantic. Specimen in photograph from Tunnell collection at TAMU-CC/CCS. See Abbott (1974); Morris (1975);Mikkelsen et al. (1995).