XXVII. On Holtenia, a genus of vitreous sponges

Abstract

During the deep-sea dredging cruise of Her Majesty’s Ship 'Lightning' in the autumn of the year 1868, the 6th of September was occupied in dredging at the depth of 530 fathoms in latitude 59° 36' N., and longitude 7° 20' W., only about 20 miles beyond the 100-fathom line of the Coast Survey of Scotland, slightly to the westward of north of the Butt of the Lews. The minimum temperature indicated by the mean of three thermometers (which registered 47°, 47°∙5, and 47°∙5 Fahr. respectively) was 47°∙3 Fahr, the surface-temperature being 52°5 Fahr. During the day there were four successful hauls of the dredge, which came up each time full of a pale-grey tenacious mud, consisting in a great measure of minute amorphous particles of carbonate of lime mixed with “coccoliths” and “coccospheres.” There was only a small proportion of the Globigerinæ and other minute Rhizopods which are so abundant and characteristic over the whole of the warm or “Gulf-stream” area of the North Atlantic. The mud was glairy, as if it had been mixed with white of egg; and it contained disseminated through it an immense quantity of extremely delicate siliceous organisms, spicules of sponges, and the shells of Radiolarians and Diatoms. Large Rhizopods of the genera Astrorhiza, Rhabdammina, Cristellaria, Cornuspira , and others were abundant; and there was a somewhat scanty sprinkling of small forms belonging to the higher groups, Echinoderms, Annulosa, and Mollusca. Besides a number of dead shells, chiefly of the Boreal or Scandinavian type, and several undescribed Echinoderms and Crustaceans, the following species were procured living.