XXI. On the echinoidea of the ’porcupine‘ deep-sea dredging-expeditions

The deep-sea dredging-cruises of H. M. Ships 'Lightning’ and 'Porcupine’ during the summers of 1868, 1869, and 1870, in the North Atlantic, were comprehended within a belt 1500 miles in length by from 100 to 150 miles in width, extending from the Færöe Islands along the northern and western coasts of Scotland and Ireland and the coasts of Portugal and Spain to the Strait of Gibraltar. In this area fifty-seven successful hauls of the dredge were made during the three summers in water exceeding 500 fathoms in depth, sixteen beyond 1000 fathoms, and two beyond 2000 fathoms. Even at the latter extreme depths Echinodermata appeared to be abundant. At 2435 and at 2090 fathoms all the Echinoderm orders were represented—the Echinoidea by a small variety of Echinus norvegicus, v. Düben and Koren, and a young example of Brissopsi lyrifera, Forbes; the Asteridea by an undescribed species of the genus Archaster; the Ophiuridea by Ophiocten sericeum, Forbes, and Ophiacantha spinulosa, Müller and Troschel; the Holothuridea by Echinocucumis typica, Sars; and the Crinoidea by a very remarkable new form of the Apiocrinidæ, which has been noticed under the name of Bathycrinus gracils, Wyville Thomson. From 2000 fathoms upwards the number of Echinoderms seems to increase rapidly; but this apparent increase may possibly be due to our greater knowledge of the fauna of shallower water; at from 300 to 800 fathoms along the coast of Britain many species of all the orders are enormously abundant, so much so as to give a very marked character to the fauna of that special zone. Several of these species (such as Cidaris papillata, Leske, Toxopneustes dröbachiensis, Müller, Echinus norvegicus, D. & K., Astropecten tenuispinus, D. & K., Archaster Parellii, D. & K., A. Andromeda, M. &T., Euryale Linkii, M. & T., and Antedon celtius, Barrett) have long been known to inhabit the deep water of the British area, and form part of a fauna which will be probably found to have a very wide lateral extension at temperatures whose minimum ranges from 0°C. to + 2º C.—a fauna which crops up, as it were, within the ordinary limits of observation in the seas of Scandinavia, and which has consequently been carefully studied by the Scandinavian naturalists.