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Show 1899.] CORALLIIDJE OP MADEIRA. 61 and the spread of the branches is nearly the same. The ramification is so dense that the coral resembles the thickly-leafed branch of a tree. In several places one layer of branches stands in front of another layer, but in both cases the polype-cells are on the anterior faces of the branches. The longer axis of the broken end of the stem measures 17 millim. There are three main branches, one of which has been broken off short, and this gives the coral a lopsided appearance. Here and there the main branches widen out in an irregular manner. This may probably be owing to the fact that boring animals have excavated the axis at these places, for in the lower part of the stem such excavations are seen where the spiculiferous ccenenchyma has been removed. Upon the specimen were seated some interesting zoophytes that rarely occur at Madeira-(1) a branched Alcyonarian (probably Suberia sp.), 100 millim. high with a spread of 80 : (2) four fine specimens of a Desmophyllum ; (3) an example of the rare Stenella imbricata (J. Y. J.), 50 millim. high, with three or four branches. 3. PLEUROCORALLIUM JOHNSONI (Gray). (Plates VI. & VII. figs. 2 & 5.) Since this species was shortly described by Dr. Gray as a member of the genus Corallium (P. Z. S. 1860, p. 127) from a specimen sent by me to the British Museum, larger and more perfect examples have occurred which supply materials for a completer account of it. In an Additional Note on this coral (P. Z. S. 1867, p. 125) Dr. Gray proposed two new genera, Pleurocorallium and Hemicorallium, assigning the present species to the latter. Later naturalists, not being able to find grounds for two genera, have abandoned one of them and placed the then single species of Hemicorallium under Pleurocorallium, as the definition of this genus in the Note cited preceded that of the other one. (See Stuart O. Ridley's valuable paper on the arrangement of the Corallihhe, P. Z. S. 1882, p. 222.) _ W h e n fully grown, the coral is much and very irregularly branched with an open system of ramification, the flexuous branches extending essentially in one plane, rarely meeting and uniting. Base spreading widely and thinly over the object to which it is attached. Axis compact, stony, white, the surface striated longitudinally ; its transverse section elliptical. Cortex (ccenenchyma) cream-coloured, frequently pitted ; at the inner surface a ring of ducts (ccenosarcal canals) surrounds the axis. Polype-cells prominent, sessile, wart-like, subhemispherical, about 2 millim. high and 2*5 in diameter; irregularly scattered on the anterior face of the branches from 1 to 5 millim. apart, sometimes in contact, especially at the tips of the branches, which are knobbed with them. The summits have a cycle of eight short lobes, which in the dry state curve over the orifice. The polype has an orange or yellow colour. Only three forms of spicula have been detected in the cortex and polype-cells:-(1) the double carafe-shaped spicule with two |