S133

Larcospira quadrangula Haeckel

Larcospira quadrangula Haeckel, 1887, p. 696, pl. 49, fig. 3; Benson, 1966, p. 266, pl. 18, figs. 7-8

DESCRIPTION "Fully developed tests subquadrangular in outline but with a sagittal constriction. Structure consisting of a double spiral representing a turning of two diagonally opposite wings of the second transverse girdle around the principal axis of the test; the other two wings of this girdle are absent. The wings are attached proximally two oppositely placed, cylindrical, polar (coaxial with principal shell axis) beams, each of which arises from the inner-most ellipsoidal shell from which is developed the inner trizonal shell surrounding it; the two spiral wings of the second transverse girdle arise from the trizonal shell. Each of the two wings are elongated parallel to the principal axis and form half-cylindroidal chambers whose openings face in opposite directions. Wings (chambers) supported by several thin, cylindrical, radial beams which arise from the surface of the inner trizonal shell. Lattice of test with subequal to unequal, subpolygonal pores, subregularly arranged, separated by thin intervening bars. Surface of test with scattered thorns or short, thin, conical spines." (from Benson, 1966).

DIMENSIONS "based on 13 specimens...length of P1 axis (innermost shell) 31-36 microns, of P2 axis (inner trizonal shell) 68-82 microns, of P3 axis (sagittal constriction of fully developed forms) 135-209 microns, of T1 axis 18-27 microns, of T2 axis 43-64 microns, of T3 axis (maximum breadth of fully developed tests) 125-246 microns" (from Benson, 1966).

Plate 17, figure 2

S134

RECENT DISTRIBUTION

1. Benson, 1966; "This species is rare in the Gulf [of California] ... Its near absence in the northern half of the Gulf indicates that it is an oceanic species."

2. Nigrini, 1970, fig. 21; belongs to a tropical assemblage derived by recurrent group analysis of North Pacific samples, but ranges too far north to be meaningful in down-core analysis.

3. Sachs, 1973, Code 201; "The species has a maximum abundance of less than 5% of sample, and is exclusively Southern in its distribution, loading on the Transitional Fauna." Southern is south of about 45 degrees N.