Nymphaster arenatus (Perrier 1881)

Nymphaster arenatus (Perrier)

Pentagonaster arenatus Perrier, 1881a:21; 1884:168, 176, 178, 179, 181, 182, 186, 236–238, pl. 7: figs. 3, 4; 1894:39.

Pentagonaster ternalis Perrier, 1881a:20; 1884:168, 180, 181, 186, 233–234, pl. 1: fig. 1.–A. Agassiz, 1888: fig. 377.

Dorigona arenata.–Perrier, 1885c:39, 40; 1885a:884; 1894:31, 32, 33, 34, 38, 39, 40, 379–382, pl. 21: fig. 5, pl. 22: fig. 6, pl. 24: figs. 5, 6.–Koehler, 1895:15; 1896:57–58, 124–125; 1909b:83, pl. 3: fig. 7.–Grieg, 1921:19–20, pl. 4: figs. 5–8.

Dorigona ternalis.–Perrier, 1885c:39, 40; 1894:39, 371–375.

Non Dorigona ternalis.–Koehler, 1909a: 54–58, pl. 8: figs. 5, 6.

Nymphaster basilicus Sladen, 1889:295, 296, 306, 308–310, 655, 693, 709, 752, pl. 57: figs. 8, 9.–Verrill, 1899:186.

Nymphaster arenatus.–Sladen, 1889:752.–Verrill, 1899:186.–Farran, 1913:11–12.–Fisher, 1919:277.–Koehler, 1924:182.–Mortensen, 1927:84–85, fig. 48.–H. L. Clark, 1941:39–40.–A. H. Clark, 1954:375.–John and Clark, 1954:139.–Halpern, 1970a:223–228, fig. 28B.

Nymphaster ternalis.–Sladen, 1889:752.–Verrill, 1899:185, pl. 26: fig. 7.–Fisher, 1919:264, 266, 268, 276, 278, 282.–A. H. Clark, 1954:375.

The general form is stellate, with a broad disc and five long, sharply tapered arms. The abactinal surface is pentagonal, and the plates are low-tabulate and irregularly round. They are covered by regularly spaced, rounded granules. The bases of the radial plates are prominently lobed. Single papular pores cover most of the abactinal surface except for a small, triangular, interradial area. The superomarginal plates, in contact medially throughout the length of the arm, number 24–64, depending on size. They are two and one-half times as wide as long interbrachially, and approximately square distally. The abactinal and lateral surfaces are at right angles to each other. They are covered by rounded, regularly spaced granules. The inferomarginal plates correspond to the superomarginals and are similarly granulated.

The large rhombic actinal plates, which do not extend beyond the third or fourth marginal, are covered with coarse, rounded, regularly spaced granules. The adambulacral plates are strongly angular (becoming apophyses beyond the actinal areas) and bear a furrow series of 6–11 moderately long, compressed spines with blunt tips. The subambulacral spines are in three or four irregular rows of 4 or 5 large granules. The mouth plates are long, narrow, and triangular; they bear 10 or 11 furrow spines slightly longer than the adambulacral furrow spines. The median spine is longest and most compressed. A row of tall, rounded spines lines the median suture; the rest of the plate is covered with scattered granules. The madreporite is tumid and covered with coarse, radiating gyri. The ocular plates are small, oval, and covered with granules. Small excavate pedicellariae, when present, occur on some of the abactinal, inferomarginal, and/or actinal plates, and two- three- or four-valved spatulate pedicellariae occur on some adambulacrals.

This species is abundant from the northern Gulf of Mexico to Brazil, in 275–3,000 meters. In the eastern Atlantic, it occurs from Ireland to Morocco and the Canary Islands.

MATERIAL EXAMINED.–Oregon II Stations: 10206 (11) [R=60 mm, r=20 mm, Rr=1:3]; 10624 (2) [R=84 mm, r=22 mm, Rr=1:4]; 10514 (1) [R=84 mm, r=22 mm, Rr=1:4]; 10844 (1) [R=75 mm, r=19 mm, Rr=1:4]; 10876 (1) [R=? (all arms broken), r=20 mm,]; 10877 (5) [R=62 mm, r=16 mm, Rr=1:4]; 10872 (1) [R=70 mm, r=15 mm, Rr=1:4.7]; 10900 (2) [R=74 mm, r=20 mm, Rr=1:3.8]; 10491 (2) [R=18 mm, r=5 mm, Rr=1:3.5]; 10602 (2); 10794 (3); 10843 (1) [R=43 mm, r=12.5 mm, Rr=1:4], Oregon Stations: 2820 (10) [R=75 mm, r=17 mm, Rr=1:4.5]; 4855 (3) [R=57 mm, r=14 mm, Rr=1:4]; 4413 (2); 1946 (1); 1885 (1); 2774 (1); 1920 (2); 6703 (3) [R=53 mm, r=13 mm, Rr=1:4]; 2005 (1) [R=74 mm, r=21 mm, Rr=1:3.6 (specimen has cluster of enlarged granules on most interbrachial marginals)]; 4416 (9) [R=35 mm, r=12.5 mm, Rr=1:2.5]; 3654 (2) [R=66 mm, r=17 mm, Rr=1:4]; 2353 (7) [R=86 mm, r=21 mm, Rr=1:4 (largest specimen and few others have small spinules on some marginals)]; 3560 (3) [R=47 mm, r=13 mm, Rr=1:3]; 1505 (4) [R=69 mm, r=18 mm, Rr=1:4]; station unknown (2); 6696 (4) [R=41 mm, r=11 mm, Rr=1:4] 2814 (5) [R=63 mm, r=16 mm, Rr=1:4]; 3574 (1) [R=90 mm, r=21 mm, Rr=1:4.5]; 489 (1) [R=19 mm, r=6 mm, Rr=1:3]; 5784 (1). Alaminos Stations: 87/69–A–11 (2) [R=67 mm, r=12 mm, Rr=1:5]; 78/69–A–11 (2) [R=70 mm, r=15 mm, Rr=1:4.5]; 11/68–A–13 (1) [R=59 mm, r=14 mm, Rr=1:4]; 2H/67–A–5 (1) [R=80 mm, r=15 mm, Rr=1:5]; 1/68–A–13 (1) [R=61 mm, r=13 mm, Rr=1:4.5]; 15H/68–A–7 (1) [R=70 mm, r=20 mm, Rr=1:3.5]; 13A/68–A–7 (1); 4E/68–A–7 (1); 15/65–A–9 (3) [R=20 mm, r=6 mm, Rr=1:3]; 24/68–A–13 (1) [R=19 mm, r=4 mm, Rr=1:5]. Combat Station: 450 (3) (small spinules on a few of the superomarginals).

Nymphaster subspinosus (Perrier)

Pentagonaster subspinosus Perrier, 1881a:21; 1884:168, 176–178, 185, 234–236, pl. 6: fig. 1.

Dorigona subspinosa.–Perrier, 1885c:39, 40; 1894:38, 39, 375–379.

Nymphaster subspinosus.–Sladen, 1889:752.–Verrill, 1899:185.–H. L. Clark, 1941:40.–A. H. Clark, 1954:375.–Halpern, 1970a:228–232, figs. 12–13.

This species is very similar to N. arenatus, except that most of the inferomarginal plates bear 1–3 short, conical spines, some of the superomarginal plates may bear a similar spine, and one or two small conical spines may occur on some of the actinal plates. I do not consider these differences as being of a specific nature, especially as many specimens of N. arenatus bear more or less conical granules on the actinal plates, and enlarged granules or incipient spines on the marginals. Two specimens collected by the Oregon off the Florida Keys in 200 fathoms could easily be assigned, one to N. arenatus and one to N. subspinosus–in fact, there is no other way one could interpret these specimens if both species are to be maintained.

MATERIAL EXAMINED.–Combat Station 450 (1) [1 (with 1 specimen of N. arenatus)]. Oregon, no station, off Florida Keys, 200 fms. [R=70 mm, r=22 mm, Rr=1:3].

Pseudarchaster Sladen

Pseudarchaster Sladen, 1885:617. [Nomen nudum.]

Pseudarchaster Sladen, 1889:109. [Type, by subsequent designation, Pseudarchaster discus Sladen (Verrill, 1899:191).]

Aphroditaster Sladen, 1889:116. [Type, by original designation, A. gracilis Sladen.]

Several rows of abactinal plates extending far along arm; usually more than one row reaching terminal plate. Unpaired (but not recurved) median spine at apex of each mouth plate pair.

Of the two species in this genus known from the western North Atlantic, only P. gracilis was taken in these collections.