N91

Stichopilium bicorne Haeckel

Stichopilium bicorne Haeckel, 1887, p. 1437, pl. 77, fig. 9; Benson, 1966, p. 422, pl. 29, figs. 1, 2

DESCRIPTION

"Cephalis smooth, cap-shaped, separated from thorax by a change in contour but in most specimens the apical-lateral arches and the ventral arch are represented by ribs which occupy slight furrows separating the cephalis from small, dorsal and ventral lobate swellings of the proximal portion of the thorax; pores of cephalis small, equal, subcircular to polygonal, regularly arranged. Two prominent, straight, nearly equal, three-bladed cephalic horns lying in the sagittal plane correspond to the dorsally ascending apical horn and ventrally ascending vertical horn. The former extends from the apical bar which in its upper portion above the junction with the apical-lateral arches is a dorsal rib in the wall of the cephalis and in its lower portion is free within the cephalic cavity. The latter extends from and in collinear with the vertical bar which joins with the ventral arch. The dorsal and primary lateral bars extend as ribs in the thoracic wall and are prolonged into heavy, equal, three-bladed winglike spines which are generally straight and diverge downward but are nearly horizontal in a few specimens; spines latticed proximally in a few tests. Thorax pyramidal with slightly concave sides between the thoracic ribs in its proximal portion; its distal portion circular in section, campanulate or inflated cylindrical; the wall of the thorax is extended outward where each of the three basal spines originate, thus giving the appearance of three latticed wings originating from the middle portion of the thorax. Number of abdominal segments variable from none to at least two; these joints separated from one another and the thorax by distinct constrictions which are generally occupied by continuous internal septal rings. Abdominal joints cylindrical, inflated, truncate conical or campanulate. Surface of thorax and abdominal joints smooth. Pores of these joints similar, of equal size, small, hexagonal to subcircular, hexagonally arranged in transverse rows. (from Benson, 1966).

"abdomen may or may not be fully developed" (Renz, 1976).

DIMENSIONS "length of test 98-193 mu; maximum breadth (thoracic or abdominal joints) 80-138 mu; length of cephalis 21-25 mu, of thorax 62-102 mu, of first abdominal joint 25-49 mu; breadth of cephalis 20-31 mu, of thorax (distal portion) 83-111 mu; length of apical horn 14-49 mu, of vertical horn 15-37 mu, of basal spines 12-53 mu." (from Benson, 1966).

Plate 26, figures la,b

N92

RECENT DISTRIBUTION

1. Benson, 1966; "... cosmopolitan but very rare in the Gulf [of California]."

2. Molina-Cruz, 1975, Code N34 not used in factor analysis of southeast Pacific assemblages; cf. Appendix 10 for percent N34 at each station.