Benthopecten simplex (Perrier 1881)

Benthopecten simplex (Perrier)

Archaster simplex Perrier, 1884:264, pl. 1: fig. 8.

Pararchaster simplex.–Perrier, 1894:254.

Benthopecten simplex.–Fisher, 1911:143.

This fragile seastar has five long, slender arms and a small disc. The thin dorsal membrane is set with small, rounded plates bearing 1–3 tiny thorny spinules. These plates are crowded on the disc, some even fused together, but are widely scattered on the arms. There are 1–10 large spines in the center of the disc. The anus is large and surrounded by a cluster of small spinules. The long, oval superomarginal plates, confined mostly to the side of the arms, have a central mammelon bearing a long, stout, thorny spine; 1 or 2 small spinules may occur near the base of this spine. The distal edge of the plate overlaps the proximal edge of the plate ahead. There is a larger odd interradial marginal, rather triangular in shape, confined wholly to the dorsal surface and bearing a single very large, acute spine. The smaller inferomarginal plates are similar to the superomarginals and alternate with them. There is almost always a large pectinate pedicellaria between all the inferomarginals. In the actinal interradial area, there is a single row of 2–6 small, rounded plates, each bearing a small acute spinule; some or all of these plates may be replaced by 1 or 2 large pectinate pedicellariae. The adambulacral plates bear six long, somewhat flattened, and blunt spines, parallel to the groove and fused at the base; on the actinal face is a single large spine and 1 or 2 small, slender spines. The mouth plates are rounded and tumid; there are a pair of stout spines at the apex, one to each jaw half, and three smaller spines on each side. There are 2–4 smaller spines on the actinal face of each jaw half. The madreporite is raised, irregular, and deeply channeled; it forms part of the base of one of the odd interradial superomarginals.

This is a deepwater species, occurring from 1,100–1,500 fathoms from Nova Scotia to the central Gulf of Mexico.

MATERIAL EXAMINED.–Alaminos Station 4/69–A–13 (7) [R=48 mm, r=6 mm, Rr=1:8]. Oregon Stations: 2572 (1) [r=9 mm (all arms broken)]; 2574 (6) [r=9 mm (all arms broken)]; 2571 (1) [R=48 mm, r=6 mm, Rr=1:8].

Cheiraster Studer

Cheiraster Studer, 1884:129. [Type, by original designation, C. gazellae Studer.]

No odd interradial marginal plate; papulae form bilobed U- or V-shaped group on disc dorsum near base of rays; dorsal plates paxillate; marginals covered with small spinules or granules; furrow spines continuous with a series of smaller spines around outer edge of adambulacral plate.

Five species of Cheiraster have been reported from the West Indies: C. mirabilis (Perrier), C. coronatus (Perrier), C. echinulatus Perrier, C. planus Verrill, and C. enoplus Verrill. Perrier (1894), Ludwig (1910), and Verrill (1915) all considered C. coronatus no more than a subspecies of C. mirabilis at most, and I am inclined to view it as well within the range of variation of C. mirabilis; the name coronatus should be considered a junior synonym of mirabilis. Based on Verrill’s (1915) descriptions, I am also inclined to believe that his C. planus is simply a large mirabilis. None of the differences he notes between the two species seem to be anything more than normal growth factors, or characters well within the range of variation. Cheiraster enoplus is readily distinguished from the other species by its numerous papular pores in paired, elongate, leg-of-mutton-shaped papularia, and by its truncate, grooved-tipped preoral spines. It usually has a dense cluster of fairly long, acute spines in the center of the disc (these may also be present in C. mirabilis). C. echinulatus seems a perfectly good and distinct species; it is quite small, with a more broadly stellate shape than the other species (Rr=1:4). It has fewer marginal plates (less than 20, as opposed to 35–60 in other species). The dorsal plates are also more distinctly paxillate.