The Zoological Results of the “Challenger” Expedition

Abstract

VOLUME XVII. of the Zoological Reports of the voyage of the Challenger contains three memoirs. The first is the second and concluding Part of the Report on the Isopoda collected during the Expedition, by Mr. Frank Evers Beddard, of which the first Part was published in 1884, and dealt exclusively with the family of the Serolidæ. The collection of Isopoda made during the voyage was very rich in new species and genera, more particularly in the deep-water forms, of which no less than thirty-eight are described as new. Among the shallow-water species the greater number of novelties were dredged off Kerguelen and the adjacent islands, adding no less than fifteen new species to the previously short list known. In other parts of the world, with the exception of Australia, dredging in shallow water did not yield any considerable number of species of the group. Many of the species described as new were previously briefly diagnosed by the author, in the Proceedings of the Zoological Society of London. Passing from the description of the species of this exceedingly interesting group of Crastacea to the summary of their distribution, we find that, while the 300-fathoms line marks approximately the boundary between what may be called the deep-sea and the shallow-water species, yet there is no trace of any zone of depth that has not its Isopod fauna. From 345 fathoms down to 2740 fathoms, species were dredged continuously; there was nowhere a break of more than 100 fathoms. In passing from the lesser to the greater depths, there is evidently a decreasing number of species that are common to these depths and to shallow water; but it is impossible to draw an absolute line of division which would separate an abyssal from a shallow-water fauna. Of the seven species found at a depth of 2000 fathoms and upwards, two range into lesser depths, another (perhaps two) into shallow water, leaving only three distinctly abyssal forms.

Report on the Scientific Results of the Voyage of H.M.S. “Challenger” during the Years 1873–76 under the Command of Capt. G.S. Nares, R.N., F.R.S., and of the late Capt. F. T. Thomson, R.N.

Prepared under the Superintendence of the late Sir C. Wyville Thomson., &c., and now of John Murray, one of the Naturalists of the Expedition. Zoology—Vol. XVII. (Published by Order of Her Majesty's Government, 1886).