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Volume 11, 1878
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Art.XL.—On a new Species of Millepora.

By the Rev. J. E. Tenison-Woods, F.L.S., F.G.S., Corr. Mem. Roy. Soc. Victoria, Tasmania, Linn. Soc. N.S.W.; Hon. Mem. Roy. Soc. N.S.W., Adelaide Phil. Soc., etc., etc. Communicated by Prof. Hutton.

[Read before the Otago Institute, 10th September, 1878.]

The specimen to which I have the honour to call the attention of the Society was sent to me by my friend Captain F. W. Hutton, of Otago, and was stated to have been found in Foveaux Strait; but the depth at which it occurred and its station were not stated. It is a tufted zoothome of highly reticulate structure, but hard and compact. It grows apparently in a solid mass, from which pencil-like cylindrical stones grow out vertically, to a height of two or three inches, but not more than a third of an inch in diameter. On examining the surface with the microscope, it is seen to be covered with minute rounded pores, which have an exact, thickened, very slightly raised margin. These pores are very close to one another, but there are interstices which are occupied by much smaller pores, which are in fact nothing but the polygonal spaces left between the closely-crowded tubes. When a fragment is broken across, two different kinds of structure are observed. One is a kind of outer ring, on which a radiate arrangement of the tubes is preserved, that is to say radiating from the axis to the circumference; the other is a central cancellous tissue, made up of tubes exactly like the surface, but the walls more delicate. The outer radiate ring of tubes is about one-fifth of the diameter; the remaining four-fifths is occupied by the central tissue. The latter is of different colour, or blueish white, while the outer ring is a reddish-brown. The tubes, which open on the outer surface, are not more than half a millimeter in depth, but it is not at first very clear whether they are closed by tapering to a point or whether they curve downwards or upwards, and so join the cancellous tissue or pith, as it might be termed, of the centre. The tubes of the centre seem to be continuous. A hair can be easily passed down them for half an inch or more. When a section is made it is then clearly seen that the tubes curve downwards, and are crossed from time to time by tabulæ or partitions, which are few in number and wide apart.

All these details point very decidedly to the nature of the organism with which we have to deal. It is a Millepore, but of an exceptional and peculiar type. Until very lately these singular corals were ranged amidst the Madreporaria tabulata. Their true character was, however, discovered by Agassiz on one of his cruises to the reefs of Florida. Prof. Dana says that he often had Millepore corals under study in the Pacific, and waited long for the expansion of the animals, but was never gratified by their making

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their appearance.* Agassiz observes that they are very slow in expanding themselves. When expanded they have no resemblance to true polyps. There is simply a fleshy tube with a mouth at top and a few small rounded prominences in place of tentacles, four of them sometimes largest. The corals of the Milleporæ are solid and strong, as much so as any in coral seas. They have generally a smooth surface, and are always without any prominent calices, there being only very minute rounded punctures over the surface from which the animals show themselves. The cells in the coralline are divided parallel to the surface by very thin plates or tables. The Milleporæ are very abundant corals. They extend outside the tropics in Australia as far south as Moreton Bay. In the West Indies they contribute largely to the formation of the reefs.

According to Professor Verrill, there are thirteen species of the genus Milleporæ known, but two of these, M. monilifornis and complanata, are supposed to be varieties of M. alcicornis and plicata respectively. Without any exception they are all tropical and living. They occur, as already stated, in the West Indies, and also in the Indian Archipelago, the Red Sea, Mauritius, and the Fiji Islands. The occurrence, therefore, of a species in New Zealand, and in so cold a latitude as Foveaux Strait, is most singular and interesting. Such facts have a tendency to make us doubt some of the geological conclusions at which we sometimes arrive. A few years ago, the discovery of two reef-building genera of corals in the tertiary beds of Tasmania was looked upon as the evidence of an almost tropical climate. Indeed, a discussion ensued at the Geological Society of London as to whether it might not be presumed that the axis of the earth had shifted since these beds were deposited. The coral to which I am now drawing attention is truly of a reef-building kind, but I am not aware whether it forms reefs. This would be a very interesting subject of enquiry. I have named the species Millepora undulosa, from the peculiar undulating character of the surface of the branches. It is thus described:—

Millepora undulosa, n.s.

Corallum-arborescent, very much branched, branches crowded cylindrical, spreading in all directions, generally somewhat flattened at the extremity and with a short bifurcation, often coalescent, either along the whole side of the branch or just at a point of contact, or by sending out a short small branchlet from one stem to another. The whole surface of the branches undulating with broad but not deep rugosities; cells exceedingly small, crowded giving a spongy appearance; colour, dull reddish-brown. Altitude of specimen described 80; width at farthest extremity of branches

[Footnote] * Corals and Coral Islands, by James D. Dana, English Edition, p. 79.

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52; diameter of branches from 3 ½ to 6; diameter of extremity of branch at bifurcation, 7 millimetres.

It is nearest in shape, dimensions, etc., to M. tortuosa, of Fiji, the only known Pacific form.

Note.—Millepora undulosa is obtained not uncommonly by the Stewart Island oyster dredgers, in from 14 to 20 fathoms of water, along with Cinctipora elegans, Pustulipora purpurascens, Idmonea radians, and other polyzoa. I am not aware that it forms anything like reefs.—F. W. H.

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