Hymenaster anomalus Sladen 1882

Hymenaster anomalus Sladen

Hymenaster anomalus Sladen, 1882:228; 1889:512, pl. 89: figs 3, 4, pl. 91: figs. 4–6.

This substellate species has a broad plane disc and five broad-based arms tapering to an acute point. The dorsal membrane consists of a dense network of thick fibrous muscle bands, forming a firmer dorsum than is usual in Hymenaster. The membrane is supported in regular rounded elevations over the whole abactinal surface; these elevations are produced by the paxillar spines, of which there are three on a short pedicel to each H-shaped dorsal plate; the three spines are not divergent, but are carried erect as a single unit. The osculum is enclosed by a ring or coronet of low papillose elevations, within which the reticulate muscle bands continue partway up the five triangular valves. The valves consist of about 5 or 6 moderately long spines; because of the fleshy covering over the spines, the exact number is difficult to determine. The spiraculae are minute and occur in the meshes of the reticulum. The actinal surface is covered with fine muscle fibers. The ambulacral grooves are wide and lanceolate, with two rows of stout, straight, untapered tube feet. The adambulacral plates bear 3 or 4 glassy furrow spines, usually webbed, either all together or in 2–2 or 2–3 groupings, and not in transverse series.

The aperture papillae are large, flat, and nearly circular; Sladen described them as small and elongate-oval, but I believe this may be variable. The actinolateral spines number about 13–17, with the sixth the longest; there is a narrow interradial area unsupported by spines, but the sixth spine on each side touches the sixth spine of the adjacent arm at the ambitus. The narrow, lateral fringe is scalloped between the actinolateral spines which protrude slightly through it. The mouth plates are small, and each bears three large, stout suboral spines. Because of the position in which this specimen is preserved, it is impossible to see the marginal edge without destroying the specimen; Sladen says this species has two small marginal spines on the oral edge of each plate.

With its relatively sturdy dorsal membrane and its partially webbed adambulacral spines, this species is almost as close to Pteraster as to Hymenaster; a new genus should probably be erected for it when additional material becomes available. For the time being, it is best left in the genus Hymenaster.

This species was known previously only from Tristan da Cunha, in 1,425 fathoms.

MATERIAL EXAMINED.—Alaminos Station 4/69-A-13. (1) [R=14 mm, r=8 mm, Rr=1:1.7].

Pteraster Muller and Troschel

Pteraster Muller and Troschel, 1842:128. [Type, by original designation. Asterias militaris O. F. Muller.]

Pterasterides Verrill, 1909:547. [Type, by original designation, Pteraster aporus Ludwig.]

Lophopteraster Verrill, 1895:203. [Type, by original designation, L. abyssorum Verrill.]

Hexaster Perrier, 1891b:1227. [Type, by original designation, H. obscurus Perrier.]

Temnaster Verrill, 1894 (as subgenus):275; 1905 (as genus): 202. [Type, by original designation, Pteraster (Temnaster) hexactis Verrill (=Hexaster obscurus Perrier).]

Muscle bands present in supradorsal membrane, but not usually reticulate; adambulacral armature in transverse webbed combs; actinolateral spines forming free, independent lateral fringe, not merged in actinal floor; small spiraculae sometimes present.

Some confusion exists about the western Atlantic tropical and subtropical species of Pteraster. Perrier’s original description of P. caribbaeus (1881b) is vague, and it is impossible to determine on which specimen he based his description. In a later (1884), more complete description, one of the two specimens from Nevis (Blake Station 151) evidently formed the basis for the description. Perrier here stated that one of the specimens was in bad shape, and at least his measurements of major and minor radii are based on the best of the two specimens. He also had three smaller specimens, badly deteriorated, from two other stations, and a sixth specimen, from Sand Key, Florida (Blake collection), which differed in important respects from the good specimen from Nevis. Obviously, this latter specimen must be considered the type of P. caribbaeus; Perrier did not designate a holotype, so the specimen now in the collection of the Museum of Comparative Zoology at Harvard bearing catalog number 957 (the “good” specimen from Nevis) is hereby designated the lectotype of Pteraster caribbaeus Perrier. The two small specimens marked paratypes of P. caribbaeus in the Museum of Comparative Zoology (MCZ 958) from Frederikstadt (Blake Station 130), along with the above-mentioned specimen from Sand Key, correspond more nearly to the type of P. militaroides H. L. Clark; it is unfortunate that Clark (1941) mentions, as the distinctive feature of P. caribbaeus, the heavy, white epioral spines. He apparently examined the Sand Key specimen, rather than the Nevis specimen. This makes all the more peculiar the fact that he described a new species in the same paper, P. militaroides, which is in fact identical with Perrier’s Sand Key specimen of “P. caribbaeus.” His specimen of P. caribbaeus, from Station 2978C, is the same species as his specimens from Cuba which he called P. militaroides. To compound the confusion, Verrill (1915) redescribed P. caribbaeus on the basis of a specimen from Albatross Station 2667, which is in fact the species later described by Clark as P. militaroides. Clark’s description of this species is wholly inadequate, and it is only by comparison of type material that the two species can be distinguished. And contrary to Clark’s statement, there is a much greater contrast between P. militaris and P. militaroides than between P. militaris and P. caribbaeus. Heavy white or hyaline suboral spines of very dense, solid calcite are not present on the lectotype of P. caribbaeus (which has large, rather blunt, and sometimes slightly curved suborals of a echinoid-like lattice-structured calcite), but are present on the holotype of P. militaroides. Other differences are discussed in the descriptions of the two species.