Page:Memoirs of the Geological Survey of Great Britain, Volume 1.djvu/373

360 the one side, and from the central portion of the German Ocean on the other.

IX. Found rarely south of the most northern of our seas, and for the most part rare even there, are certain species which mark the near approach of an Arctic or sub-Arctic province. Such are, Margarita undulata, Natica groenlandica, Fusus albus and Sabini, Buccinum Donovani, Astarte borealis, and Terebratula cranium. They are associated with zoophytes of equally Arctic character. Many of the species enumerated under the last type are much more abundant, and finer, in the northernmost province, of which they are truly members—their distribution southwards being occasional and in isolated patches, the nature of which I shall hereafter explain.

Our native Radiata have a similar distribution with the Mollusca, though, perhaps—owing to the great powers of locomotion which many of them possess, either in their perfect or else in their larva state—not so well marked. The coral Turbinolia milletiana (discovered by Mr. MacAndrew, alive, off the Cornish coast, hitherto known only as fossil) and the Echinus lividus, Thalassema Neptuni, and Syrinx nudus, are examples of the southernmost types. Comatula rosacea, Ophiura texturata and albida, Ophiocoma rosula and neglecta, Uraster glacialis, Palmipes membranaceus, Asterina gibbosa, Asterias aurantiaca, Echinocyamus pusillus, Spatangus purpureus, Cucumaria pentactes, and Syrinx nudus, among the Echinodermata, and Pennatula phosphorea, Alcyonium digitatum, Actinea effæta, Laomedea gelatinosa, Sertularia pumila and many hydroid zoophytes, Cellepora pumicosa, Tubulipora serpens, and many ascidioid zoophytes, are representatives of the third or European type. So also are such Medusæ as Aurelia aurita and granulata.

The Celtic type is seen in Uraster rubens, Solaster papposa, Echinus sphæra and miliaris, Amphidetus cardatus and roseus, Thyone papillosa and Echiurus vulgaris, Actinea mesembryanthemum, senilis and dianthus, Flustra foliacea, Antennularia antennina, Plumularia falcata, and many Sertulariæ and other hydroid and ascidioid zoophytes.

The British type is represented by Ophiocoma brachiata, and minuata, Uraster hispida, Syrinx Harveii, several corneous zoophytes, as, Thuaria articulata and Plumularia myriophyllum, Actinea bellis, Anthea tuediæ, Capnea sanguinea, Iluanthus scoticus? Cellepora Skenei, and many other ascidioid zoophytes. I doubt whether any of our Medusæ come properly under this head.

The Atlantic type is represented by certain zoophytes, among which are Carophyllia Smithii, Plumularia pennatula, and Eschara foliacea.

The Oceanic type is instanced by such Medusæ as Velella and Diphyes, occasional visitants of our western shores.

The Boreal type has numerous members among the Radiata.