Camptoplites rectilinearis

"Camptoplites rectilinearis sp.n. Plate XII, fig. 4; Figs. 51 D, 52 A–D.

STATION DISTRIBUTION. Antarctic: Victoria Quadrant, St. 1660.

GEOGRAPHICAL DISTRIBUTION. Ross Sea (Terra Nova, Sts. TN 314, TN 339; Discovery).

HOLOTYPE. St. TN 339.

DESCRIPTION. Colony (Plate XII, fig. 4) consisting of long straight branches with many series of zooecia (eleven counted in some branches).

Rootlets arising from lateral and axillary chambers with runners, axillary rootlet arising from frontal or distal surface of chamber and projecting frontally (Fig. 52 A).

Zooecia very long and narrow (Fig. 51 D), with nearly straight sides, borders of aperture overlapping neighbouring zooecia very slightly. Marginal zooecia usually with outer distal corner pointed.

Spines present on some fertile zooecia, slender and directed frontally, otherwise absent.

Avicularia of two kinds both with moderate stalks (Figs. 52 A–C). Small ones round-headed with lower head-angle about 90°. Larger ones long-headed with lower head-angle acute, not so large as those of Camptoplites retiformis and C. latus.

Ovicells usually longer than wide, entooecium radially striated when young (Fig. 52A), a slight roughening or punctate sculpture being superimposed later, ectooecium mostly uncalcified, its only frontal calcification (if any) being in its distal part (Fig. 52 D).

REMARKS. In basal view the lateral walls of the zooecia are nearly parallel throughout their length. In frontal view (Fig. 51 D) the straight-sidedness of the zooecia is less conspicuous because the borders of the aperture slightly overlap the neighbouring zooecia. The basal surface commonly bears fine transverse striations, which appear curved as they follow the contour of the wall, but these are sometimes, though less frequently, seen in related species.

It might be thought that the direction of the rootlets (in which C. rectilinearis agrees with C. reticulatus and C. areolatus) would depend on the position in which the par­ticular colony was growing, but it is so consistent in the material of Camptoplites examined by me that I regard it as a specific character.

Branches with as many series of zooecia are found in C. retiformis and C. latus, and long narrow zooecia are sometimes seen, particularly in C. retiformis, but they are not usual in these species. In the direction (but not the distribution nor the size) of the spines, in the shape of the avicularia, and in the long stalks of the large avicularia, C. rectilinearis resembles C. retiformis. The ovicells are larger than those of either C. retiformis or C. latus, and differ from them in sculpture." (Hastings, 1943: 462)