Siphonochelus longicornis: Shell translucent white when young, waxen with areas of pale rosy brown between the varices in the adult; varices four, ascending the spire nearly in a straight line; tubes tapering, recurved, usually broken off short, but originally long; nucleus subglobular, glassy, followed by seven gradually increasing whorls, obscured by the varices, but somewhat scalar behind; surface with extremely fine spiral striation, stronger lines of growth, and on the tips of the tubes and canals when fresh a glassy polish; varices not fimbriated, with rounded edges, strongly arched forward, subconcave behind; aperture small, subcircular, margin detached from the body, elevated, not sharp; with simple edge and smooth interior; canal long, slender, nearly straight, but bent back as a whole, with three antecedent canals surrounding a sort of umbilical chink. Operculum muricoid. Max. length of shell, 23.0 mm; of last whorl, 19.0 mm; of aper¬ture, 4.0 mm; of canal before the aperture, 11.5 mm; max. lat. of aperture, 3.0 mm; of shell, 10.0 mm.

Siphonochelus longicornis: The shell is of moderate size (maximum length 24 mm) and fusiform. The spire is high, consisting of one and one-half bulbous, translucent nuclear whorls and six convex postnuclear whorls. The suture is impressed. The body whorl is moderately large and fusoid. The aperture is small and subcircular, with an erect peristome. The upper corner of each varix and adjoining partition is swept dorsally, forming a moderately long, hollow, dorsally swept anal siphonal tube connecting the varix to the preceding whorl. The siphonal canal is long and barely angled dorsally, consisting of a moderately broad upper one-third and a lower, slender, tubular two-thirds. The body whorl bears four sharp varices, these (as noted above) swept dorsally at their upper (i.e. posterior) ends. The crest of each varix is weakly dorsally reflected. Immediately below each anal tube there is a single inconspicuous cusp or weak point on the varical margin. Spiral sculpture is essentially lacking. Shell color is waxy white, with suffusions of fleshy to rosy brown between varices. The leading edge of the varix and the interior of the aperture are invariably white, and the siphonal canal is translucent.

Siphonochelus longicornis: This species is allied to T. fistulosus Brocchi, T. arcuatus Hinds, and the related forms above mentioned. It has wider varices than the former, and a proportionally smaller aperture; T. fistulosus appears to be destitute of the fine spiral striation, has a more distorted appearance, and does not reach so large a size. T. longicornis is much more fusiform, attenuated, and has longer tubes and canal than T. arcuatus.

Siphonochelus longicornis: Caribic. Straits of Florida and off Cuba in deep water (350-600 m).