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The Atoll of Funafuti, Ellice group : its zoology, botany, ethnology and general structure based on collections made by Charles Hedley of the Australian Museum, Sydney, N.S.W.

[XIII.] — The Sponges of Funafuti

page 323

The Sponges of Funafuti.

The collection of sponges obtained by Mr. C. Hedley, though small, is nevertheless interesting.

There are sixteen species; of these the following six are described as new—Spinosella glomerata, Gellius aculeatus, Clathria pellicula, Agelas gracilis, Ciocalypta incrustans, and Polymastia dendyi.

Of the above Agelas gracilis is the most interesting, as it widens the range of the genus. With the exception of an outlier recorded from Mauritius and doubtfully from Tristan d'Acunha, this genus has hitherto only been known from the West Indies.

The remaining ten species are—

Reniera australis, Lendenfeld, Reniera sp.* which may prove to be a variety of Reniera rosea, Bowerbank, Halichondria solida, var.

rugosa, Ridley and Dendy, Echinodictyum asperum, Ridley and Dendy, of the latter rare and curious species there are two very fine examples, Acanthella stipitata, Carter, A. pulcherrima, Ridley and Dendy, Spirastrella papillosa, Ridley and Dendy, Euspongia irregularis, var. silicata, Lendenfeld, Hippospongia dura, Lenden-feld, and Spongelia fragilis, var. irregularis, Lendenfeld.

The species in many cases are represented by single examples.

The smaller specimens had been placed in a solution of four or five p.c. formol, which proved insufficient for their proper preservation. They reached me in a soft and slimy state, too soft in fact to handle with safety, and before a hand-section could be cut they had to be hardened in alcohol. In consequence of their imperfect preservation and their transference to alcohol, the specimens had some of their characters destroyed, which rendered their exact determination unusually difficult.

Mr. Hedley has kindly supplied the following field notes:—

"To a collector accustomed to the sea beaches of temperate zones, and especially to the shores of Sydney Harbour, the absence of large or conspicuous sponges on the reefs of Funafuti is very marked. Rocky shelves and ledges which in England or page 324temperate Australia would be clad by a luxuriant growth of sea-weeds and sponges, are here almost entirely monopolised by a rank growth of Sarcophytum and its allies.

An expert in spongology would doubtless reap a rich harvest on these reefs by cracking loose, dead coral blocks and securing those minute forms which hide themselves in numerous crevices. But a superficial survey of the rocks from high water mark to a depth of twenty feet, impresses on the observer that the oft described wealth and profusion of life on a coral strand is not equally true of all classes. The larger sponges, at any rate, contribute handsomer, more highly coloured, more numerous and varied forms to a sea-scape in Port Jackson, than they do in the Ellice Islands.

About low water mark the most conspicuous sponge was, perhaps, the coal-black Euspongia irregularis, var. silicata, growing in cake-shaped masses on the rocks. In similar situations spinosella glomerata flourished. Among the Sarcophyta, from which, indeed, a casual glance hardly distinguished it, the Hippospongia dura encrusted the rocks. From a depth of thirteen fathoms in the lagoon the dredge came up almost choked with Echinodictyum asperum, with which the urchins Laganum and Maretia were associated.

Nearer the centre of the lagoon, in about twenty fathoms, were dredged the new Clathria pellicula, encrusting a cluster of cocks-comb oyster. This was only taken on one occasion.

The Reniera sp. was extremely plentiful in pools in the mangrove swamp, where alone it was met with. It flourished alike in shade and sunlight. At a distance it sometimes appeared as large rose-pink patches, many yards in extent, creeping under stones and climbing on mangrove roots. When deprived of light the beautiful rose-pink tended, under the shelter of the mangrove, to fade into gray. Each sponge mass attained a height of eight or ten inches, and a diameter of about a foot. In the open the growth was reduced to a prostrate network of tubes."

* Identical with No. 42, Voy. "Alert," p. 410.