The United States Coast Survey has, in connection with an exploration of the Gulf Stream, been the first to establish a systematic series of dredgings at great depths, continued during several years. The results have proved conclusively that there exists everywhere, in the deep sea, modified, of course, according to the nature of the bottom and the temperature, a most varied fauna, totally distinct from that characteristic of the shores and of shallower waters. Since 1867 Count Pourtales has had charge of these investigations, first established many years ago by Professor Bache and continued by his successor Professor Peirce. He has dredged across the Gulf Stream between Florida and Cuba to a depth of about seven hundred fathoms, collecting an immense number of marine animals entirely unknown before, and characteristic of the different belts of depth, having a most extraordinary geographical distribution, many of the species being found in Florida, the Azores, the Faroe Islands, and the west coast of Norway. The English Admiralty has for two summers detailed a vessel admirably fitted for such purposes, intrusting the scientific direction of the expedition to Dr. Carpenter, Professor Thomson, and Mr. Jeffreys. Their dredgings, carried on to the enormous depth of two thousand four hundred and thirty-five fathoms, have in every respect corroborated the conclusions drawn from the collections made by Count Pourtales and the Scandinavian naturalists, who, not content with so thoroughly exploring their own coast, have even sent a ship of war to dredge across the whole Atlantic. These discoveries only show how much yet remains to be done before we shall fully understand the laws of marine life. But we already have ample evidence that the same beneficent order controls the distribution of animals in the ocean as on land, appointing to all its inhabitants their fitting home in the dim waste of waters. * * * * * SYSTEMATIC TABLE OF THE ANIMALS DESCRIBED IN THIS VOLUME RADIATA CUV. CLASS I.--POLYPI LAM. ORDER I.--ACTINARIA EDW. _Metridium marginatum_ EDW. _Rhodactinia Davisii_ AG. _Bicidium parasiticum_ AG. _Arachnactis brachiolata_ A. AG. _Halcampa albida_ AG. ORDER II.--MADREPORIA AG. _Astrangia Danæ_ AG. ORDER III.--HALCYONARIA EDW. _Halcyonium carneum_ AG. CLASS II.--ACALEPHÆ CUV. ORDER I.--HYDROIDEA JOHNST. _Velella mutica_ BOSC. _Physalia Arethusa_ TIL. _Nanomia cara_ A. AG. _Millepora alcicornis_ LIN. _Hydractinia polyclina_ AG. _Tubularia Couthouyi_ AG. _Hybocodon prolifer_ AG. _Coryne mirabilis_ AG. _Turris vesicaria_ A. AG. _Bougainvillia superciliaris_ AG. _Dysmorphosa fulgurans_ A. AG. _Dynamena pumila_ LAMX. _Dyphasia rosacea_ AG. _Lafoea cornuta_ LAMX. _Melicertum campanula_ PÉR. et LES. _Ptychogena lactea_ A. AG. _Laomedea amphora_ AG. _Zygodactyla groenlandica_ AG. _Tima formosa_ AG. _Eucope diaphana_ AG. _Clytia bicophora_ AG. _Oceania languida_ A. AG. ORDER II.--DISCOPHORÆ ESCH.