S125

Tetrapyle octacantha Muller

Tetrapyle octacantha Muller, 1858, p. 33, pl. 2, figs. 12, 13, pl. 3, figs. 1-12; Benson, 1966, p. 245, pl. 15, figs. 3-10, pl. 16, fig. 1, text-fig. 18

DESCRIPTION "Complete tests consisting of two well-defined systems of latticed dimensive girdles, with few, if any radial beams, and a third outer system of poorly defined girdles supported by numerous short beams of approximately equal length that arise from the nodes of the intervening bars of the latticed girdles of the second system. Most tests incomplete, consisting either of all or a portion of the second girdle system (transverse and lateral girdles with rudimentary, sagittal girdle), but in several tests with some indication of the third girdle system in the form of numerous branched spines or incomplete outer girdles, generally representing the rudimentary, third transverse girdle. Pores of the latticed girdles relatively large, unequal, irregular to subregular in arrangement, generally subcircular to subpolygonal. Surface of complete specimens irregular, rough or spinose; surface of second girdle system relatively smooth to highly spinose. Outline of second lateral girdle generally ellipsoidal (major diameter the principal of P axis) but variable from subcircular to subquadrate. Gates defined by the transverse and lateral girdles of the second system generally elliptical to kidney-shaped, in a few specimens with beams lying in their plane and joining the transverse girdle with the rudimentary second sagittal girdle. Radial beams absent in many tests but when present generally lie in the axes of the test (P, T, or S), although in a few specimens they extend from the pole of the inner system of girdles at an acute angle with the axis. Beams arise from the inner ellipsoidal shell or ring but do not penetrate beyond the second girdle system as free spines; number of coaxial beams variable but generally six when present; a few specimens were observed with only one of a pair of opposide polar beams extending through the inner tubular space between gates; rarely more than one beam observed at each pole; tests without beams generally with short polar spines or thorns representing rudimentary beams. Specimens with eight diagonal spines, each originating from one of the eight edges of the second transverse girdle (Tetrapyle octacantha Muller) rare, with or without polar beams." (from Benson, 1966).

DIMENSIONS "range in length of dimensive axes of each girdle system (cf. fig. 18):

...Range (microns).....Range (microns)...........Range (microns)

P1.......14-18..............T1.......9-12............... S1..........5-9

P2.......39-65.............T2.......31-48..............S2..........15-25

P3.......93-194..........T3.......70-156.............S3..........55-95

P4.......215-246.......T4.......172-221...........S4...........21-221"

(from Benson, 1966).

Plate 16, figures 3a,b

S126

"outermost girdle length: 120 +/- 24 microns, width: 83 +/- 22 microns, next-to-outermost girdle length 42 +/- 7 microns; width: 26 +/- 8 microns" (from Sachs, 1973).

REMARKS

1. Benson (1966) suggests a lengthly synonymy based on the belief that many described species are in fact incomplete specimens or orientations are other than frontal.

RECENT DISTRIBUTION

1. Benson, 1966; "...a predominant member of the Gulf [of California] assemblage. It occurs in greatest abundance in the southern part..."

2. Sachs, 1973 (code 5I); "An important (to 18%) constituent of the Southern [south of about 45 degrees N] fauna; loads on the Transitional (Southernmost) factor."

3. Molina-Cruz, 1975, Code S54 ; counted together with Octopyle stenozona Haeckel and used in factor analysis of southeast Pacific assemblages; cf. Appendix 10 for percent S54 at each station.

4. Robertson, 1975; "This species loads quite heavily in factor 2 (subtropical). Its highest abundances are to the south at present. The region in which it is absent at present is significantly further to the south at 18,000 YBP."