(Fig. 2 A, 3, 6A–D, 8)
Material examined. Holotype ― NIWA 62046: 3 nautical miles east of North Cape, north-eastern tip of Northland, 34.412 ° S, 173.149 ° E, RV Kaharoa, 133–210 m, 19 Apr 1999, additional vouchers of the holotype are in the CRRF reference collection (0 CDN 6695 -M) and at the USNM (USNM 1182994).
Type locality. North Cape.
Distribution. Known only from the type locality.
Description. Tall vase-shaped sponge, 200 mm high x 120 mm wide, with a 40 mm thick body wall (Fig. 2 A). Ectosome is 1.5–3 mm thick and clearly differentiated from the underlying choanosome. Margin of bowl is thinner than the body wall and slightly undulating. Surface is smooth, granular to the touch. Oscules and ostia not visible with unaided eye, texture is firm, barely compressible, interior highly siliceous, can be torn relatively easily from margin to base. Colour in life is light grey, interior tan. Colour in ethanol medium brown, interior tan.
Skeleton. Ectosome is 1500–3000 µm deep, cavernous, diaphanous, well differentiated from the underlying choanosome by a wispy 50–100 μm thick layer of granular cells (Fig. 3). Outer ectosome has a thin, dispersed crust of amphisanidasters, below which these are only lightly scattered. Dichotriaenes form a rough radiating layer in the ectosome, with cladomes protruding slightly beyond the surface. Choanosome is dense and heavily pigmented, dichotriaenes also form an irregular, roughly radial to oblique layer at the choanosome/ectosome boundary (Fig. 3), interspersed with oxeas. Microscleres are sparsely scattered throughout the choanosome.
Spicules. Megascleres (Fig. 6 A–B) are oxeas (Fig. 6 A), very large, stout, slightly curved, 2004 (1825–2552) x 34 (21–50) μm; dichotriaenes (Fig. 6 B) with stout, conical rhabdome, 723 (453–897) μm long, cladome width 347 (183–461) μm, protoclads 82 (63–109) μm long, protruding forward at an angle of approximately 45 °, deuteroclads slightly longer than protoclads, 100 (44–154) μm.
Microscleres (Fig. 6 C–D) are oxyasters (Fig. 6 C), choanosomal, with 4–6 very stout acanthose rays, 35 (28– 43) μm diameter; amphisanidasters (Fig. 6 D), with a short thick axis and numerous short conical acanthose spines protruding in a cluster from each end, or from along the shaft. Spines are frequently of different lengths, 11 (10–13) μm.
Substrate, depth range, and ecology. Attached to deep rocky reef interspersed with sandy substrate, between 133– 210 m.
Etymology. Named for the vase-shaped morphology of the species (poculum = Latin for cup or bowl).
Remarks. Stryphnus poculum sp. nov. has the same general skeletal, cellular arrangements, and spicule categories as the type species S. niger from Port Jackson, South Australia; it has a well demarcated diaphanous ectosome, short-shafted dichotriaenes, large oxeas, oxyasters and amphisanidasters. However, the spicule dimensions differ considerably between the two species; S. poculum sp. nov. has smaller oxeas and amphisanidasters, but larger dichotriaenes and oxyasters than S. niger (Table 3). Furthermore, the dichotriaenes of S. poculum sp. nov. are present in both the ectosome and choanosome, unlike in S. niger where they are confined to the ectosome. The two species are easily separated on field characters; S. poculum sp. nov. is a tall, light greyish brown cup-shaped sponge whereas S. niger and all other known species, with the exception of S. ponderosus (Bowerbank 1866) are massive, lobate, or thickly encrusting. Stryphnus ponderosus from the Arctic and Atlantic coasts of Europe sometimes forms a cup or goblet but its amphisanidasters have longer, thinner spines than those of S. poculum sp. nov.