Cancellaria panamuna: Protoconch 1,5 smooth, slightly deviated convex whorls, nucleus slightly submerged, translucent, microscopic growth lines, merging gradually into adult sculpture. Teleoconch 4 convex whorls, finely cancellate; body-whorl 70 per cent of total length. Sutures well impressed. Sculpture of fine vertical axial ribs, about 50 on penultimate, crossed by transverse striae equal in strength to ribs, 8 on penultimate, about 18 on body-whorl, with one fine thread between each paii; ribs are finely nodular at intersections; whole sculpture crossed by microscopic growth lines. Umbilicus absent. Aperture elongate-ovate, contracted both ends, a very short siphonal canal; columella straight with 3 strong oblique plaits; inner-lip reflected as heavy white glaze on to body-whorl; outer-lip regularly curved, thick and heavy but sharply edged, 17 internal lirations. Colour off-white. Dimensions. Holotype, length 17-2 mm, breadth 6-9 mm. Fully mature.

Cancellaria panamuna: The only other species occurring in Australian waters which may be confused with this is Fusiaphera dampierensis, which is smaller but with similar but coarser sculpture, a much larger and more depressed protoconch, and the axis of the aperture much further inclined from the vertical. Compared with C. (Sydaphera) purpuriformis Valenciennes (below), this new species has many fine vertical axial ribs compared with the low oblique flattened ribs of C. (S.) purpuriformis, and the many fine transverse grooves in the latter species are replaced by fine raised striations, nodular at intersections with ribs.

Cancellaria panamuna: Type locality. 28 km N.W. of Anchor Island, off Onslow, Western Australia (21° 15' S., 114° 38' E.), 119 metres. Distribution. Type locality, and 14 km N. of Long Island, near Onslow (21° 37' S., 114° 38' E.), also 161 km N. of Croker Island, Northern Territory (9° 30' S., 132° 34' E.), 77 to 124 metres.