Shell small, rather solid, lanceolate. Colour uniform white. Whorls eight, including the protoconch. The latter has two and a half whorls, the first two being smooth and helicoid ; the next half whorl carries about ten sharp, narrow, arcuate, radiate riblets, quite discordant with the succeeding sculpture. The adult whorl begins abruptly with seven prominent ribs, which descend the whorls vertically and continuously; these are traversed by spaced spiral cords which commence with two on the third whorl and end with seventeen on the last. Between these cords run from two to six rows of densely packed microscopic grains. Aperture sublinear ; the thick and outstanding varix extends a broad lip over the mouth ; sinus semi-circular, cut out of the varix, with a substantial tubercle on the right and another on the left; there are no other teeth within either lip ; on the columella is a thick and smooth sheet of callus. Length 5 mm., breadth 2 mm.

The interstitial rows of granules are extremely fine and number up to 10 per spiral interval (rather than 'two to six rows' as given by Hedley). The main spiral lirae number 3 on the penultimate whorl, plus (as a rule) 1-2 weaker ones posterioriv; they are rather evenly spaced, and even on the rostrum are only slightly closer. Apart from the parietal tubercle mentioned by Hedley, in most of the paratypes the upper part of the columella bears two weak nodules, and the outer lip, in addition to a conspicuous posterior denticle, may show traces of vestigial denticles anteriorly.

Two not fully grown specimen are in hand, characterized by 1) biconic-claviform shell 4 mm high, 2) protoconch conical of 3 convex whorls, the last axially ribbed, 3) teleoconch whorls subangular, 4) body whorl rapidly tapering at the base, 5) anal sinus apparently shallow, asymmetrical and 6) sculpture of 7 strong collabral ribs, overriding fine spiral cords and dense spiral rows of microscopic granules; 3 spiral cords and a weaker adapical one occur on spire whorls, 16 on body whorl (including the weaker most adapical one). The species resembles Pseudorhaphitoma drivasi Kilburn, 1993, and Pseudorhaphitoma phaea (Melvill & Standen, 1901) in the general shell shape, but has a different protoconch and sculptural details.
DISTRIBUTION AND HABITAT. Pseudorhaphitoma bipyramidata is distributed from South Africa to Australia and northward to Japan. Occurrences are from fine-grained substrates, in the 9-139 m depth range.
FOSSIL RECORDS. None recorded.

There is a species from the Persian Gulf which, though rather larger, seems to be otherwise identical, and which has been distributed as Mangilia fairbanki and as Maugilia scitula, neither of which names are applicable. I have also seen P. bipyramidata, from the Isle of Pines, New Caledonia. Along the Great Barrier Reef this species seems common and generally distributed.

Range: Australia: Queensland 5 to 8 fathoms, Great Barrier Reef; Murray Island (type) ; 4 to 14 fathoms, Albany Passage; 5 to 10 fathoms, Hope Island; 15 fathoms, Palm Island ; 4 fathoms, Van Diemens Inlet, Gulf of Carpentaria 20 fathoms, off Endeavour Reef.