S137

Lithelius nautiloides Popofsky

Lithelius nautiloides Popofsky, 1908, p. 230, pl. 27, fig. 4 (only); Riedel, 1958, p. 228, pl. 2, fig. 3 (only), text-fig. 2; Petrushevskaya, 1967, p. 53, figs.27; 28, I; 29, I

DESCRIPTION "Shell subspherical, consisting of a small, spherical medullary shell surrounded by a completely involute spiral of approximately four or five whorls. The whorls of the spiral increase in width outward, and are penetrated by numerous radial bars which extend as radial spines on the shell surface. Radial spines mostly broken off in the examples from the sediments, but according to Popofsky they are approximately as long as the shell radius or shorter, needle-like, and of varying thickness. Shell wall of moderate thickness, with rounded pores of different sizes." (from Riedel, 1958).

DIMENSIONS "Diameter of medullary shell 10-15 m, of entire shell of approximately four to five whorls 110-220 m" (from Riedel, 1958).

REMARKS

1. Petrushevskaya (1967) suggested that only one of Popofsky's illustrations is L. nautiloides. She refers the other specimens which have only 2 or 3 whorls, rather than 5 or 6, to Lithelius sp.

2. According to Petrushevskaya, there is some doubt about the generic placement of this species since the type species (L. spiralis Haeckel, 1860) has a double spiral rather than a single one. However, Benson (1966) and the present authors agree that L. spiralis has a single spiral and, therefore, the generic assignment is acceptable.

Plate 17, figure 5

S138

RECENT DISTRIBUTION

1. Lozano, 1974(Fig. IV-20); "This species seems to be slightly more restricted in its distribution than other Antarctic species; it is always present under Antarctic waters and generally present under southern subantarctic waters. When found close to or north of the subtropical convergence it is generally as a product of reworking or northern transport by bottom waters.

"It reaches a maximum abundance of 1.58 percent of the total Radiolaria in core V14-64A.

"It also shows a good correlation with topography when found more than 2 ° north of the APF indicating northward transport by bottom currents. It generally constitutes less than 1.0 percent of the total Radiolaria except for two cores (V14-64A and RC13-253). Maximum August temperature under which it is found is 15 ° C but specimens are in place probably under surface waters below 8 ° C." 7 '