S83

Euchitonia elegans (Ehrenberg)

DESCRIPTION

"Similar to Euchitonia furcata, but differing in the shape of its arms. Arms slender, tapering distally, and sometimes terminating in 1 or 2 short, fairly stout spines. Angle between paired arms of E. elegans generally small than that of E. furcata.

"A patagium may or may not be present. When well developed it forms a delicate meshwork around the central structure and between each of the 3 arms (generally less well developed between paired arms). Meshwork forms rows of chambers, convex outwards in larger angles, concave between paired arms, and thickens towards its outer edge. Sometimes patagium shows partial development or, often, only a few initial branches are present. In other specimens there is no indication of a pagatium forming...

"It is usually difficult, if not impossible, to distinguish between E. elegans and E. furcata. These species are differentiated by the shape of the arms of faily complete and well-developed specimens. However, the majority of specimens found are either broken or not completely developed, making it impossible to identify them to species. One is tempted to make E. elegans and E. furcata and the indeterminant forms conspecific, but the difference between end members of such a series is sufficiently great to indicate that two species are, in fact, involved. Thus, a few specimens definitely belonging to each species and a large number of unidentifiable fragments were present in the samples examined." (from Nigrini, 1967).

DIMENSIONS "Average length of arms (measured from center of innermost sphere) 147-289 microns (usually 200-289 microns). Maximum breadth of arms 35-63 microns. Angle between paired arms 54 degree - 75 degrees." (from Nigrini, 1967).

REMARKS 1. For a more complete synonymy see Nigrini, 1967 and Ling and Anikouchine, 1967.

2. Benson's (1966) description and dimensions of this species (p. 230) are not consistent with the above.

Plate 11, figures 1a,b

S84

RECENT DISTRIBUTION

1. Nigrini, 1967, fig. 18, 19; "Indian Ocean occurrences - Recognizable specimens of E. elegams (fig.18) very sparsely distributed in low latitudes and do not occur in middle latitude samples ...

"Euchitonia sp. (fig. 19 is fairly abundant (4% to 12% of the described population) in low latitudes, but like E. elegans it is absent from samples taken south of 35 degrees S. The three forms appear to be reliable and potentially useful members of the low latitude assemblage."

2. Nigrini, 1968, text-fig.14; Euchitonia spp. is "Rare in the northernmost sample examined, few in the region of the Peru Current, generally several along the coast of Central America and in the region of the South Equatorial Current, common to abundant in the western part of the study area."

3. Nigrini, 1970, fig. 18; belongs to a tropical assemblage derived by recurrent group analysis of North Pacific samples, but the species does range as far north as 40 degrees N in the western Pacific.

4. Sachs, 1973, Code 22I; Euchitonia spp. (counted together with E. furcata); "their distributions are all Southern (Transitional) and they are all rare." Southern is south of about 45 degrees N.

5. Molina-Cruz, 1975, Code S12; counted together with E. furcata and used in factor analysis of southeast Pacific assemblages; cf. Appendix 10 for percent S12 at each station.

6. Robertson, 1975; counted together with E. furcata; "E. elegans is by far the less frequently occurring of these two species....

"These species load most heavily in factor 2 (subtropical). At the present they are absent north of about 45 degrees N but to the east of 165 degrees E they occur only rarely south of 45 degrees N. At 18,000 YBP they occur only rarely north of 35 degrees N."

7. Morley, 1977 (Euchitonia spp.); Fig. I-17 counted together with E. furcata; "Although these two species are placed in one taxonomic group for this study, E. furcata was much more abundant in all samples than E. elegans... These species load highest in factor 1 (tropical). Today they are most frequently found in samples from tropical regions and are absent from all samples south of 35 degrees S. At 18,000 YBP they occur only rarely in the eastern equatorial samples and are absent south of 15 degrees S."