S135

Lithelius minor Jorgensen

Lithelius minor Jorgensen, 1889, p. 65, pl. 5, fig. 24; Benson, 1966, p. 262, pl. 17, figs. 9-10

DESCRIPTION

"Ellipsoidal to spherical test consisting of 3-7 or more concentric trizonal shells, separated by approximately equal distances (6-25 microns); in certain orientations internal structure appears as a double spiral. Shells supported by thin radial beams which arise from the nodes of the intervening bars of the lattice, therefore, several hundred in number; outermost shell with thorn or thin conical spines (incipient beams for support of an additional shell) arising from the nodes of the intervening bars; spines generally short (5-20 microns), but long (up to 40 microns) in a few specimens. Pores of all shells of nearly the same size, with regular to subregular arrangement, subcircular to subpolygonal, 9-15 of half the minor circumference of the outermost shell." (from Benson, 1966).

"As noted by Benson, forms may exhibit either doubly spiral shells or concentric shells, depending of their orientation. In either case, there are generally less than four whorls or shells. The form is one of the most heavily constructed encountered in this study." (from Sachs, 1973).

"In general the specimens found north of the subtropical convergence have more shells, four to seven, most frequently four to five, whereas under southern subantarctic waters specimens with three to four shells are most common. Small specimens 80 microns in diameter are found together with the largest ones (140 microns). As noted by Benson (1966) when specimens are turned under the microscope the internal structure appears as distinct concentric shells..., or as a double spiral ..., and in certain oblique positions as a spiral. The position in which it appears as a single spiral is very unstable, it is very difficult to photograph and it never adopts this orientation in permanent slides." (from Lozano, 1974).

DIMENSIONS

"major diameter of test 79-148 microns, minor diameter 70-132 microns." (from Benson).

"major diameter: 103 +/- 17 microns; minor diameter 90 +/- 14 microns." (from Sachs, 1973).

REMARKS 1. For a more complete synonymy see Benson (1966).

Plate 17, figures 3, 4a,b

S136

RECENT DISTRIBUTION

1. Benson, 1966; "... cosmopolitan in the Gulf [of California]..."

2. Sachs, 1973, Code 8I; "Almost ubiquitous, and important (to 9% of fauna). Concentrated in southernmost (Transitional) and bottom-influenced factors."

3. Lozano, 1974, Fig. IV-10; "Generally absent south of the APF, when present it constitutes less than one percent of the total Radiolaria. It is always found in samples under subantarctic and subtropical waters in proportions varying from 0.1 to a maximum of 8.0 in core V29-80.

"As could be expected from its morphological variability, it does not show a clear pattern of latitudinal distribution within the subantarctic and subtropical waters."

4. Molina-Cruz, 1975, Code S24; "This species appeared very cosmopolitan. It probably needs a taxonomic review, since the specimens may represent more than one species with markedly different ecological responses."; used in factor analysis of southeast Pacific assemblages; cf. Appendix 10 for percent S24 at each station.