S93

Spongaster tetras tetras (Ehrenberg)

Spongaster tetras Ehrenberg, 1860b, p. 833; 1872b, p. 299, pl. IV(iii), fig. 8

Spongaster tetras tetras Ehrenberg, Nigrini, 1967, p. 41, pl. 5, figs. 1a, b (with synonymy); Riedel and Sanfilippo, 1978a, p. 74, pl. 2, figs. 2-3

DESCRIPTION

"Shell is a square with rounded corners. Four spongy, pear-shaped 'arms' approximately at right angles, are regularly placed in one plane around 5 concentric lattice spheres. A completely enveloping patagium usually makes the central spheres difficult to see, and, at best, 5 concentric rings can be recognized; the 'arms' appear merely as dark patches.

"Patagium is, for the most part, a dense irregular spongy meshwork with small subcircular pores, but around the "arms" bars become thicker and 3-bladed. In some specimens radial beams apparently form a basis for the patagium which will then have a radially striated border. Patagium may be depressed slightly around the central structure, but at its periphery its thickness is approximately 0.25 the length of the sides of the square." (from Nigrini, 1967).

DIMENSIONS "Distance between sides 150-302 microns (usually 150-276 microns); diagonal 187-369 microns (usually 187-316 microns)." (from Nigrini, 1967).

REMARKS

1. For a more complete synonymy see Nigrini, 1967.

2. Benson's (1966) description of this species (p. 238) is consistent with the above, but his dimensions are generally smaller (e.g., length of diagonal 127-196 microns) which may reflect lack of affinity for restricted water masses such as the Gulf of California.

Plate 13, figure 1

S94

3. "Additional illustrations can be found in Riedel and Sanfilippo, 1971, pl. 1D, figs. 2-4." (Nigrini, pers. comm., 1994).

RECENT DISTRIBUTION

1. Benson, 1966; "This species is rare at all Gulf [of California] stations where it is present... Because it is present at only four stations in the northern half of the Gulf, its greater affinity for oceanic water masses is indicated."

2. Nigrini, 1967, fig. 20; "Indian Ocean occurrences- S. tetras tetras is fairly abundant in the western tropics, but decreases in abundance east of 85 degrees E, and is absent from middle latitude samples. It appears to be a reliable and potentially useful member of the low latitude assemblage."

3. Nigrini, 1968, text-fig. 15; "Absent from the northernmost sample examined, rare or absent in the region of the peru Current, few in the regions of the North and part of the South Equatorial Currents; common in a broad region which includes the Equatorial Countercurrent and part of the South Equatorial Current."

4. Nigrini, 1970, fig. 19; belongs to a tropical assemblage derived by recurrent group analysis of North pacific sediments, but the species does range as far north as 40 degrees N in the western Pacific.

5. Molina-Cruz, 1975, Code S40; used in factor analysis of southeast Pacific assemblages; cf. Appendix 10 for percent S40 at each station.

6. Morley, 1977; Fig. I-18; "This species loads highest in factor 1 (tropical). At present the species is most abundant in the tropical waters of the western Atlantic. The position of the 0% contour at 18,000 YBP would seem to indicate a similar distribution pattern when compared to today's values."