Comprehensive DescriptionRead full entry
(Plate I., fig. 5, and Plate IV., figs. 1-7.)
Rossella racovitvæ, Topsent (11, p. x., and 12, p. 33).
The collection contains only one example of this species, which appears, however, to have been common in the region explored by the ‘Belgica,’ since no less than ten specimens and fragments were obtained in four hauls.
The present specimen is 16 mm. in length and 13 mm. in breadth, not including the pleuralia, which extend 8 mm. from the surface.
The ‘Discovery’ specimen differs in several respects from those described by Topsent.
The principalia are diactins with roughened rounded ends, sometimes swollen.
The autodermalia are pentactins and stauractins, hexactins being absent; the rays are thick, slightly spined and a little swollen at the ends.
Just below the surface, along with the oxypentactins, are many thick curved diactins 1080 x 12µ.
The oxyhexasters are not remarkable except in the smallness of their numbers; they appear to be replaced by the discohexasters.
The calycocomes are 225 µ in diameter, whereas those of the ‘Belgica’ are 400 µ.
The discohexasters, 168 µ in diameter, are very abundant; the large disks at the ends of the secondary rays attain a diameter of 16-20 µ, and have long sharp denticles; these spicules present all the transitions from holodiscohexasters, through hemi- to mono-discohexasters.
The microdiscohexasters (rare), 56 µ in diameter, have the secondary rays of only one length.
‘Discovery,’ Winter Quarters, Flagon Point, January 17,1903; Dredge 18-36 m. (10-20 fathoms).
The ‘Belgica’ Expedition dredged it in Lat. 70° 15’-71° 15’ S. Long. 80° 48’ - 87° 39’ W. 450-569 m. (247-310 fathoms).”