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Plectopyramis dodecomma Haeckel, 1887

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Plectopyramis dodecomma, n. sp.

Shell smooth, slenderly pyramidal, with straight outlines. Cephalis conical, obtuse with thirty-six small square pores (in nine devergent longitudinal rows, each of four pores). Collar septum (between cephalis and thorax) with four distinct collar pores. Thorax pyramidal, with nine very stout and straight angular radial beams, which are connected by ten to fifteen broad horizontal nine-angled rings. Each of the large regular, square meshes so produced contains a very delicate fenestration with twelve regular, square pores, separated by two transverse and three longitudinal threads. A very regular and remarkable structure.

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax (with ten rings) 0.2 long, 0.15 broad.

Habitat.—Central Pacific, Station 217, depth 2425 fathoms.
Haeckel 1887
Benson, 1966, p. 424-426; pl. 29, fig. 3:

Plectopyramis dodecomma Haeckel

Plectopyramis dodecomma Haeckel, 1887, Challenger Rept., Zool., vol. 18, p. 1258, Pl. 54, fig. 6.
?Bathopyramis quadrata Haeckel, 1887, op. cit., p. 1159, Pl. 54, fig. 1.
?Bathopyramis trapezoides Haeckel, 1887, op. cit., p. 1160, Pl. 54, fig. 3.
?Cinclopyramis infundibu1um Haeckel, 1887, op. cit., p. 1161, Pl. 54, fig. 7.
Sethopyramis quadrata Haeckel, 1887, op. cit., p. 1254, Pl. 54, fig. 2.

Test consisting of a small subhemispherical, poreless cephalis, with or without apical horn or spine, and smooth, long, conical thorax, broad at the base, consisting of 8-11 heavy, longitudinal bars or ribs, circular in section, and joined by transverse bars, likewise circular in section, that are continuous around the circumference, straight not curved between adjacent longitudinal ribs. Thoracic pores subrectangular, increasing in size toward the base; in the proximal one-third of the thorax the pores are either infilled by silica or by a thin, reticulate, secondary meshwork. Collar pores not observed in all tests, but at least three are present and four if vertical bar is developed. Apical spine variable from absent, to a short spine, to a heavy, conical horn either straight or curved. Vertical spine not observed but may be present in some specimens. One specimen observed with a raised thoracic rib corresponding to one of the primary basal spines and extending for about one-third the length of the thorax.

Measurements; based on 7 specimens from stations 27, 34, 46, 56, and 60: maximum length of test 160-277 µm; maximum breadth of thorax 117-178 µm; length of cephalis 10-16 µm; breadth of cephalis 11-17 µm; length of apical spine or horn 0-37 µm.

Remarks. This species differs from Peripyramis circumtexta Haeckel in the absence of branched spines arising from the thorax and in the presence of transverse bars that are continuous around the circumference.
The species which have been placed tentatively in synonymy with this species differ either in the supposed absence of a cephalis (Bathopyramis quadrata, B. traezoides, Cinclopyramis infundibulum) or in the absence of a secondary meshwork developed within the large thoracic pores (Sethopyramis quadrata, Bathopyramis quadrata, B. trapezoides). The latter feature was observed to be an intraspecific variation in the Gulf specimens. It is my opinion that a cephalis is present in all of these species and that Haeckel did not recognize it. Riedel (1958, p. 231) emended the genus Peripyramis Haeckel (without cephalis) after he observed the presence of a cephalis in its type species P. circumtexta; he also states that subsequent thorough examination will probably prove that many of Haeckel's forms of this group supposedly lacking a cephalis actually have one present. Because the cephalis is small in this group, it might have been easily overlooked.

Distribution. This species is very rare in the Gulf but occurs as far north as station 184. It is relatively more abundant in the southern Gulf; therefore, it has a greater affinity for tropical Pacific waters than for Gulf waters.
Little information is available on its world-wide distribution. Haeckel (1887, p. 1258) reported it from the central Pacific "Challenger" station 271. The other species listed in the synonymy occur in the central or northern Pacific except for Cinclopyramis infundibulum which was observed from the tropical Atlantic. Based on these meager data it may be confined to tropical seas only.
Benson 1966
Benson, 1983, p. 506-507:

Plectopyramis dodecomma Haeckel

Remarks. The specimen identified as Plectopyramis dodecomma and illustrated by Nigrini and Moore (1971, pl. 21, fig. 5) appears to represent a different species for the following reasons: (1) the thorax flares distally, producing a more trumpet-like than conical shape, (2) the transverse bars of the thoracic meshwork are not continuous around the circumference, and (3) the thoracic surface has scattered spines. Their specimen is probably conspecific with one illustrated by Renz (1976, pl. 7, fig. 3) that she identified as Bathropyramis sp.
Benson 1983


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