IV. Note on syringammina, a new type of arenaceous rhizopoda

Abstract

The specimens to which the following note refers were dredged in the Faroë Channel in the autumn of last year, during the cruise of H. M. S. “Triton,” and were sent to me for examination by Mr. John Murray, F. R. S. E., under whose direction the scientific observations of the expedition were carried out. It is now a well-known fact that the region lying between the north coast of Scotland and the Faroë Islands possesses certain features of unusual interest owing to the existence, side by side, of two sharply defined areas, of which the bottom temperature differs to the extent of 16° or 17° Fahr. The depth of the two areas is very similar, ranging from 450 to 640 fathom s, and they are separated by a narrow ridge having an average depth of about 250 fathoms. The physical aspects of this phenomenon have been the subject of much discussion, and the biological conditions attendant thereupon are of almost equal importance; indeed, so far as the Rhizopoda are concerned, there are few areas of the same extent that have so well repaid the labour of investigation. On the 44 "Lightning” Expedition of 1868, supei-intended by Dr. Carpenter and Sir Wyville Thomson, the cold area furnished amongst other interesting organisms, the large Lituoline Foraminifer Reophax sabulosa, a form which has since been obtained near the same point on the cruise of the "Knight Errant," but has never been met with elsewhere. The warm area yielded at the same time Astrorhiza arenaria, a large sandy species previously unknown to British naturalists. On the "Porcupine” Expedition of 1869, another modification of the latter genus, Astrorhiza crassatina was obtained in the cold area; and near the boundary line an entirely new arenaceous type was dredged, to which the generic named Botellina has been assigned by Dr. Carpenter. From the fact that all the specimens of the form appeared more or less broken, it has been inferred that the tests were adherent when living; but the fragments were abundant and consisted of stout tubes, many of them upwards of an inch in length, the interior being subdivided by a labyrinth of irregular sandy partitions. More recently, in 1880, on the cruise of the “K night Errant,” the rare genus Storthosphœra was found in the warm region and in the cold area specimens of Cornusjpira which measured more than an inch in diameter, rivalling in size the finest of the tropical Orbitolites, and therefore amongst the largest known Porcellanoug Foraminifera.