N49

Pterocanium sp.

DESCRIPTION

Cephalis hemispherical with closely spaced pores or pits and bearing 2 stout 3-bladed or conical horns. Horns are equally well-developed, the same length as or slightly longer than cephalis; a third needle-like by-spine is frequently present also.

Thorax conical or with a slight shoulder bearing subcircular, hexagonally framed pores which increase in size distally and are usually arranged in longitudinal rows. Surface may be thorny.

Three well-developed, 3-bladed feet, latticed proximally and tapering distally. Feet are divergent, convex outwards as long to half again as long as thorax.

Abdomen, when present, consists of one or two rows of pores adjacent to thorax. (unpublished data, Nigrini)

DIMENSIONS Based on 8 specimens; length of thorax and cephalis 83-107 mu; maximum breadth of thorax 83-107 mu. (unpublished data, Nigrini).

REMARKS

1 . This species was called D. infabricatus Nigrini by Moore (1974). It differs from that species by having a distinct thoracic termination and is, as Moore noted, more robust.

2. Haeckel (1887, pl. 73, fig. 15) described a species, Pterocanium bicorne, which may be synonymous with our Pterocanium sp. However, the shape of the thorax in Haeckel's specimen is more biretta-shaped than any we have observed. On the other hand, we have not observed any other form with two equally developed apical horns. It would be necessary to examine topotypic material before adopting the name bicorne for the species here described.

Plate 23, figures 6a,b

N50

RECENT DISTRIBUTION

1. Nigrini, unpublished data; cosmopolitan, but rare throughout the North Pacific (at least).

2. Molina-Cruz, 1975; cf. D. infabricatus herein. It is uncertain whether Molina-Cruz counted D. infabricatus, Pterocanium sp. or both species together.