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Euchitonia sp. cf. E. furcata Benson, 1966

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Benson, 1966, p. 228-230; pl. 13, fig. 4, fig. 5(?):

Euchitonia cf. furcata Ehrenberg

?Euchitonia furcata Ehrenberg, 1872a, Akad. Berlin, Monatsb. (1872), p.308; 1872b, Akad. Berlin Abhandl. (1872) P1. 6 (3), fig. 6.

Distinctly bilateral test with one larger odd arm whose axis bisects the smallest of the three angles between the arms. Central region of test circular, consisting of 3-5 concentric, discoidal, latticed shells with somewhat irregular outlines. Arms club-shaped, narrower proximally than distally, with rounded terminations. Internal structure of arms consisting of 4-14 irregular concentric rings, indistinct in specimens with thicker arms; in most specimens the arms appear spongy, in a few the terminations of the arms were observed with 2-3 concentric discs. Test enveloped by a latticed sheath. Patagium generally incompletely developed, rarely completely absent, consisting of a layered spongy structure of similar thickness throughout its extent.

Measurements; based on 30 specimens from stations 46, 71, and 81: angle A 125°-141°, mean 132°; angle B 78°-117° mean 95°; angle C 118°-147°, mean 133°; ratio of angle A to B 1.07-1.73, mean 1.40, of angle C to B 1.01-1.88, mean 1.41; diameter of outer concentric shell of central region 59-98 µm; length of odd arm 43-141 µm, of each of the two similar arms 37-138 µm and 33-141 µm; minimum breadth of odd arm 38-80 µm, of each of the two similar arms 38-68 µm and 37-70 µm; maximum breadth of odd arm 55-148 µm, of each of the two similar arms 49-138 µm and 49-134 µm; length of base of triangular test 99-307 µm, of altitude 140-302 µm.

Remarks. This species differs from Euchitonia elegans and E. mülleri [=Euchitonia sp., Benson, 1983] in having shorter arms that are broader and thicker in relation to their length and in a patagium that is of similar thickness throughout its extent. The distinction between arms and patagium in specimens of this species is less clear than in those two species.
Identification of this species with Euchitonia furcata Ehrenberg is tentative because of Ehrenberg's poor illustration (1872b, P1. 6 (3), fig. 6) which does not show details of the internal structure of the arms. It also appears to be an incompletely developed form, but in symmetry and shape of the arms it is similar to the Gulf species. Because Ehrenberg reported this species from the Pacific near the coast of California, it is not unlikely that it is present in the Gulf of California. The only other Gulf species with which his species may be identified is E. mülleri Haeckel [=Euchitonia sp., Benson, 1983].

Distribution. Of all the species of "family" B, this species has the greatest frequency in the Gulf. It is cosmopolitan, being absent only at stations 203 and 214. It is common at several stations, namely, 71, 92, 93, 95, 99, 130, 184, and 194. Its highest frequency was observed at stations 184 (3.4%), 194 (3.4%), and 99 (3.2%). At station 130 its frequency is 3.9%, but the total population is only 179; therefore, this station is not directly comparable to the others. Its increased frequency at stations 184 and 194 indicates its tolerance for waters with greater than average salinity and temperature. Across the Gulf from stations 90-99, it undergoes a general increase from west to east, being rare at stations 90 and 91 but common at the other stations, reaching a maximum at station 99 which may reflect its response to upwelling along the eastern margin. In the remaining stations of the southern half of the Gulf this species is rare, being common only at station 71. It is therefore cosmopolitan in the Gulf with its local distribution controlled in part by upwelling.
Because this species, was only tentatively identified with Euchitonia furcata Ehrenberg, which was reported from the Pacific Ocean near California, little can be stated about its world-wide distribution. It has not been reported from high latitudes; therefore, it is probably confined to tropical and possibly temperate regions.
Benson 1966
This species differs from Euchitonia furcata in having shorter arms that are broader and thicker in relation to their length, in having a patagium that is of similar thickness throughout its extent, and in having a central structure consisting of three to five concentric, discoidal, latticed shells with somewhat irregular outlines.
Benson 1983











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