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Deep-Sea Echinoderms of New Zealand

Benthopecten Verrill, 1884 — Benthopecten pentacanthus sp. nov. Plate 1, Figs. D, E (holotype)

Benthopecten Verrill, 1884

Benthopecten pentacanthus sp. nov. Plate 1, Figs. D, E (holotype).

Diagnosis: Superomarginals each carrying two spines, one of which is enormously enlarged on each of the five unpaired interradial supermarginal plates. Abactinal intermediate plates each carrying one, or occasionally two similar, spinules. Inferomarginals each carrying one erect spine, plus one or two secondary spinules. The unpaired inferomarginal carrying three larger and two smaller spines. Adambulacral armature of three furrow spines and two subambulacral spines. Oral plates each with four furrow spines, the median one enlarged, plus two suboral spines.

Material Examined: Two specimens, both from the same locality, depth 400 fathoms, off Mayor Island, Bay of Plenty, Dom. Mus. Station B.S,210, 28/2/1957, R. K. Dell.

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Remarks: Both specimens are juvenile forms, as evidenced by their smaller size, and the fact that neither pedicellariae nor actinal intermediate plates arc developed. Benthopecten styracius Fisher, from Macassar Strait, would seem to be the species most closely related, and differences in the number of furrow spines (7–8 in B. styracius) and in the oral armature, could well be due merely to immaturity of the New Zealand material. However, Fisher expressly draws attention to the fact that B. styracius has only one spine on each supermarginal, whereas B. pentacanthus, despite its immaturity, already has two. Again, in styracius there are two inferomarginal spines, of which the uppermost is the longer, whereas in pentacanthus there are usually three inferomarginal spines, the lowermost being the largest. Another Pacific species, Benthopecten polyctenius Fisher, is somewhat similar, but lacks the five giant spines of the unpaired superomarginals.

Holotype: In the Dominion Museum, Wellington. R 5 mm, r 2 mm.