Narcissia trigonaria Sladen 1889

Narcissia trigonaria Sladen

Narcissia trigonaria Sladen, 1889:414, pl. 65: figs. 5–8.–Verrill, 1915:97.–H. L. Clark, 1921:58.–Brito, 1962:3, pl. 1: fig. 9–Tommasi, 1966:244.–Gray, Downey, and Cerame-Vivas, 1968:147, fig. 20.

Narcissia trigonaria var. helenae Mortensen, 1933a:429, fig. 10a, pl. 20: figs. 4–6.

This distinctive species is well represented in the collection by a good growth series showing the progressive reduction in relative size of the disc, and the development of the arms from flat and plane in small specimens to high and triangular in cross section, with a marked carinal ridge, in adult specimens. In small specimens, the carinal plates are large and in a regular row; they are irregular and obscure in larger specimens. Papular pores occur singly, none below the inferomarginals, and none in a narrow interradial band on the disc. Both marginal series are regular, even, and large, and are mostly confined to the lateral arm surface.

A single regular row of actinal intermediate plates extends to the end of the arm; in most specimens, each bears one or two small sugar-tongs pedicellariae between flat-sided granules. Similar pedicellariae occur also on many of the marginal plates and on most of the larger abactinal plates as well. The two valves of the pedicellariae are long, delicate, and slender, with 2 or 3 small terminal teeth. All plates are covered with flattened polygonal granules, those of the actinal surface coarser than those of the abactinal surface. The adambulacral plates bear a furrow series of 4 or 5 thick, blunt, somewhat flattened spines; the five subambulacral spines are thicker and broader, subprismatic, but shorter than the furrow spines; behind them is a row of 3–5 prismatic spinules or enlarged granules. These three rows of spines are on distinct “terraces” of the adambulacral plates. The mouth plates bear a crowded marginal row of huge, blunt, triangular spines, constricted at the base; behind them is a similar shorter row of spines, and behind them are three short, prismatic spines on each jaw half. The madreporite is small and inconspicuous, near the apex of one interradius. The oculars are nearly round, rather large, and bare (save for a few terminal tubercles) in the adult, but covered with fine granules in small specimens.

This species is distributed from North Carolina to Brazil, in 20–50 fathoms. Although most of the specimens in this collection are small, the species reaches a size of more than 200 mm (R).

MATERIAL EXAMINED.—Oregon II Station 10517 (4) [R=70 mm, r=8 mm, Rr=1:9 (height of disc=16.5 mm)]. Oregon Stations: 5739 (1 juvenile) [R=24 mm, r=6 mm, Rr=1:4 (height of disc=4 mm)]; 2086 (1) [R=69 mm, r=11 mm, Rr=1:6.5 (height of disc=14 mm)]; 2250 (4) [R=74 mm, r=9 mm, Rr=1:8 (height of disc=16 mm)]; 5023 (2 juvenile) [R=20 mm, r=6 mm, Rr=1:3 (height of disc=4 mm)]; 2248 (1) [R=51 mm, r=9 mm, Rr=1:6 (height of disc=12 mm)]; 5700 (1) [R=88 mm, r=21 mm, Rr=1:4 (height of disc=25 mm)].

Two other Ophidiasteridae, Leiaster lymani (A. H. Clark, 1948) and Hacelia superba H. L. Clark (1921), have been described from the area covered by this report (Key Largo, Florida, and Barbados, respectively), but were not taken in these collections.

This order is characterized by having prominent, unkeeled mouth plates; there is no definite and distinct marginal frame; pedicellariae are usually absent, but if present, they consist merely of grouped spines. The aboral skeleton may be reticulate, imbricate, or absent, and in many forms the plates are pseudopaxillate; the principal plates are often cruciform. Ambulacral plates are not crowded. The tube feet, generally in two rows, have well-developed sucking discs.

The undefinable family Poraniidae, represented in this collection by the genera Poraniella and Marginaster, is not included in the key that follows.