Shell fusiform, adults 68-172 mm long, spire 0.70-0.85 times higher than aperture in adults, diameter/height ratio 0.32-0.51 (mean 0.42, n= 14), thickness variable. Protoconch white; teleoconch creamy white, fine yellowish brown bands at summits of some or all larger spiral cords, interior porcellaneous white. Protoconch of 2.75-3.00 whorls, smooth or with indistinct spiral lines, width 3.4-4.5 mm (typically about 4 mm), first half whorl rapidly expanding. Teleoconch of up to 7.5 whorls, typically all with rounded, nodular, median, peripheral angulation and concave ramp; the side more or less flat on spire, broadly convex below, smoothly merging with broadly concave canal. Some specimens with angulation and nodules vanishing after fourth or fifth whorl, after which whorls rather evenly convex. Angulation and nodules in some (intermediate) specimens vanishing after fourth whorl then reappearing and progressively enlarging on last adult whorl. Axial costae strong, rounded, 10-12 on fourth whorl, occupying abapical two-thirds on first 4 or 5 whorls, thereafter as progressively enlarging peripheral nodules, or vanishing. Numerous crowded spiral cords throughout, multiplying by intercalation, low, narrow, broadly angulate in section, separated by grooves. Aperture plus canal narrowly pyriform. Outer lip rapidly thickened and strongly and extensively lirate within. Inner lip smooth, thickened or with rounded callous near insertion, elsewhere thin or of moderate thickness. Anterior siphonal canal of moderate length, straight or gently flexed. Fasciole very weak. Operculum and gross radular morphology typical of the genus. Central tooth with 3 small cusps, lateral teeth with 3 strong cusps, outermost cusp of lateral teeth long and slender, inner edge of inner cusp weakly crenulate.

Penion lineatus differs from P. sulcatus in having a larger protoconch (width 3.65-4.40 mm, versus 2.25- 3.00 mm, finer spiral sculpture, less crowded axial costae on the early teleoconch whorls, which are more evenly developed across the whorls (stronger adapically), a more weakly flexed anterior siphonal canal, and typically a weaker fasciole. Penion lineatus differs further from P. sulcatus in having a morphotype similar in both shape and size to the common form of the southern species P. ormesi (Powell, 1927). Penion lineatus resembles P. cuvierianus (Powell, 1927) in protoconch size and shape (Figure 2D; Table 1), but differs from the northern forms of that species in having a considerably less prominent peripheral angulation and weaker spiral sculpture, especially on the early whorls. The outer cusp on the lateral teeth of the radula of P. lineatus is considerably longer and narrower than in P. cuvierianus, P. sulcatus and P. jeakingsi (Powell, 1947) (Powell 1929, figs 122-124; Ponder 1973,

New Zealand. King Bank, Middlesex Bank, Three Kings Islands and northwest of Cape Reinga (with certainty not further south than 34°25.0'S, 172°27.8'E), 77-246 m, taken alive at 77-173 m.
Material examined
Type material (see above). Other material. 33°57.0'S, 172°19.0'E, King Bank, NE of Three Kings Islands, 128 m (1 juvenile, M.153271); 34°01.2'S, 171°44.4'E, Middlesex Bank, NW of Three Kings Islands, 206-211 m (2 juveniles, M.153268); 34°02.0'S, 171°44.0'E, Middlesex Bank, 246-291 m (1 juvenile, M.I 53267); 34°02.1'S, 171°45.8'E, Middlesex Bank, 221-206 m (1 juvenile, M.153269); 34°16.4'S, 172°15.4'E, SE of Three Kings Islands, 138-143 m (2 juveniles, M.075084).
The identification of a new, extant species of Penion increases the diversity of the genus in New Zealand. Penion lineatus n. sp. has the smallest, most restricted distribution of any living member of the genus, whereas all other local Penion species have much larger geographic ranges (Ponder 1973; Powell 1979; NMNZ http://collections.tepapa.govt.nz/). Future research should acquire molecular data from P. lineatus n. sp. in order to determine its evolutionary relationship with other taxa.
The identification of a new species of Penion restricted to the cold waters north of Cape Maria van Diemen supports the view of the region as a marine biodiversity 'hotspot'. The region is home to the present Penion species, as well as three endemic species of Cominella Gray, 1850 (Willan 1978; Donald et al. 2015) which, like Penion, is a buccinoid genus with many otherwise widely distributed species in New Zealand and Australia (Ponder 1973; Powell 1979; Donald et al. 2015). The presence of these and many additional endemic species in the region suggests that there is a significant drive for speciation there, whether through local opportunity and adaptation, or by a restriction of dispersal and gene flow. A main dispersal limiter seems likely to be the local
cooling due to upwelling. Some of the endemic marine taxa may be derived from cold-adapted southern lineages that moved northward during the glacial maxima and persisted in local cool conditions following recovery during interglacials. High marine invertebrate diversity and endemism north of Cape Maria van Diemen warrants further investigation.