S101

Stylodictya aculeata Jorgensen

Stylodictya aculeata Jorgensen, 1905, p. 119, pl. 10, fig. 41; Petrushevskaya, 1967. p. 35, pl. 17, figs. 1-3.

DESCRIPTION

"Species very similar to [S. validispina]. Differentiated by greater irregularity of structure of shell, which has effect upon disposition of chambers, radial cross-pieces, needles, and pores. In addition, in S. aculeata width of chambers increases more markedly towards periphery of disk than in previous species. S. aculeata differs from S. validispina also in larger number of pores lying across width of one chamber (4-5.5).

"Species S. validispina and S. aculeata are very similar to each other. Their morphological differences may prove to be due only to different hydrological conditions and that these are two subspecies of one polymorphic genus. The two species are very similar to S. gracilis Ehrenberg, 1854 (the type species of genus Stylodictya Ehrneberg, 1847), but differ from it by their finer, less frequent, less regularly disposed radial needles." (translated from Petrushevskaya, 1967).

DIMENSIONS "Diameter of middle chamber 15-17 microns, diameter of first ring 30-35 microns, of second about 55 microns, of third about 80 microns, of fourth 110-120 microns, diameter of disk with five rings about 150 microns." (translated from Petrushevskaya, 1967.)

Plate 13, figures 3, 4

S102

RECENT DISTRIBUTION

1. Benson, 1966; see S. validispina.

2. Sachs, 1973; this form was recognized as having "a much smaller number of rows of chambers and consequently...wider chamber rows than characterize typical S. validispina"; not counted by Sachs.