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Euchitonia triangulum
(Ehrenberg, 1872)
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Description - Add description
Benson, 1966, p. 226-228; pl. 12, fig. 7, pl. 13, figs. 1-3:
Euchitonia cf. echinata Haeckel
?Euchitonia echinata Haeckel, 1887, Challenger Rept., Zool., vol. 18, p.536, P1. 43, fig. 11.
Arms distinctly bilaterally disposed, an odd arm generally distinguishable. Central region circular, consisting of 5-8 concentric discoidal shells; arms generally broad proximally with broader but blunt, thicker terminations, characteristically with 1-5 or more (generally 12) conical to pyramidal terminal spines, continuous inwards as beams, lying in the plane of the disc, variable in length (4-31 µm). Internal structure of arms with distinct, regular, equally spaced, concentric, latticed rings, traceable from arm to arm, 6-20 per arm; terminations of arms appear spongy, suggestive of a structure similar to the central region, i.e., concentric shells. Test covered by a distinct latticed sheath as in the preceding species [Dictyocoryne profunda]. A spongy, layered patagium between the arms generally absent or only rudimentary, thinner and more delicate proximally.
Measurements; based on 30 specimens from stations 27, 34, 46, 56, 60, 71, and 81: angle A l20°-l46°, mean 131°; angle B 79°-113°, mean 99°; angle C l22°-l41°, mean 130°; ratio of angle A to B 1.06-1.85, mean 1.33, of angle C to B 1.12-1.71, mean 1.32; diameter of outer concentric shell of central region 68-107 µm; length of odd arm 37-129 µm, of each of the two similar arms 43-112 µm and 41-116 µm; minimum breadth of odd arm 49-79 µm, of each of the two similar arms 44-79 µm and 41-80 µm; maximum breadth of odd arm 69-135 µm, of each of the two similar arms 54-119 µm and 55~121 µm; length of base of triangular test 146-265 µm, of altitude 151-276 µm.
Remarks . The distinguishing features of this species are the terminal spines, when present, and the distinct regular concentric rings of the arms and regular concentric shells of the central region. This species differs from Euchitonia echinata Haeckel only in the presence of fewer terminal spines (1-5 vs. 30-40) on the arms. Because this species is rare in the Gulf sediments, its complete range of variation may not be included in the above description; therefore, it is only tentatively identified with Haeckel's species.
Distribution . This species has a spotty distribution throughout the Gulf and is very rare at all stations where it is present. It does, however, occur as far north as station 208, indicating its near cosmopolitan nature. It is absent at stations 64, 90, 95, 130, 133, 151, 191, 194, 203, 206, and 214. Its distribution does not appear to be controlled by upwelling. It apparently is an oceanic species with tolerance but no great affinity for the Gulf waters.
Haeckel reported E. echinata from "Challenger" station 253 in the north central Pacific (approximately 40° N. latitude). It has not been reported from high latitudes.
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