Prof. W. Thomson on the Deejj-sea Dredging-expeditions. 301 



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 depth Echinodermata appeared to be 

 abundant. At 2435 and at 2090 fathoms all the Echinoderm orders 

 were represented — the Echinidea by a small variety oi Echinus norvegi- 

 cus, D. & K., and a young example of Brissopsis lyrifera, Forbes ; 

 the Asteridea by a species of the genus Archaster ; the Ophiuridea 

 by Ophiocten sericeum, Forbes, and Ophiacantha spinulosa, M. & T. ; 

 the Holothuridea hy Echinocucumis typica, Sars ; and the Crinoidea 

 by a very remarkable new form of the Apiocrinidse, which has been 

 described under the name of Bathycrinus gi'acilis, Wy. T. From 

 2000 fathoms upwards the number of Echinoderms seems to increase 

 rapidly ; but this apparent increase may possibly be due to our wider 

 knowledge of the f'aima of the 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, Toxojmevstes drobachiensis, Miiller, 

 Echinus norvegicus, D. «& K., Astropecten temnspinus, D. & K., 

 Archaster Purellii, D. & K., A. Andromeda, M. & T., and Enryale 

 Linkii, M. & T., have been long 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 + 2° C, a fauna which crops up, as it 

 were, within the ordinary limits of observation in the seas of Scandi- 

 navia, and which has consequently been carefully studied by the 

 Scandinavian naturalists. 



Another group of species, including Tripylus fi'agilis, D. & K., 

 Ctenodiscus crispatus, Retzius, Pteraster militaris, M. & T., Am- 

 phiura abyssicola, Sars, Antedun Eschrichtii, O. F. Miiller, and 

 several others, are members of the same fauna described from locali- 

 ties in the seas of Scandinavia and Greenland, but not hitherto 

 known as British. A third section, consisting of a number of unde- 

 scribed Echinideans, Asterideans, and Ophiurideans, may probably 

 also belong to this fauna ; while a fourth group, likewise undescribed, 

 and including such forms as Porocidaris, Phormosoma, Calve?-ia, 

 Pourtalesia, Neolampas, Zoroaster, Ophiomusimn, Pentacrinns, 

 Rhizocrinus, and Bathycrinus, would rather appear to be referable 

 to a special deep-sea fauna of which we as yet know only a few ex- 

 amples, and with whose conditions and extension we are unacquainted. 

 This abyssal fauna is of great interest, inasmuch as nearly all the 

 hitherto discovered forms referred to it show close relations to family 

 types of Cretaceous or early Tertiary age, and hitherto supposed to 

 be extinct. 



Twenty-seven species of Echinidea were procured during the 

 cruises of 1868, 1869, and 1870, off the coasts of Britain and Portu- 

 gal, at depths varying from 100 to 2435 fathoms. 



