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.
[XVII] — The Mollusca. — Part I.—Gasteropoda
Many of the introductory remarks which prefaced collections previously dealt with, apply with equal force to the Mollusca. Little was known of the Mollusca of the Ellice Group prior to our Expedition. With one exception, none of the naturalists—Dana, Whitmee, Woodford, Finsch—who have been to the archipelago, gathered any shells. The exception being Dr. Ed. Graefie, who visited most of the atolls in the interest of the Godeffroy Museum. The land shells he procured are described by Mousson.* A few other animals described by German authors from this group were probably also collected by him.
The poverty of the fauna of the atoll, compared with that of any continental area lying under corresponding latitudes, such as Queensland, New Guinea, or the Melanesian Plateau, again asserts itself. Whole groups, the Brachiopoda and the Polyplacophora, are missing, giving to the fauna an unsymmetrical aspect. Especially significant is the absence of Mollusca with large eggs such as Nautilus, Melo, or Voluta from this drifted fauna. In many cases the Funafuti shells are smaller than the usual stature of their respective species. Harper Pease has remarked that the marine Gasteropoda of the Paumotus are in general dwarfed in comparison with those of Tahiti.† Shipley mentions that specimens of Gephyrean worms from Funafuti were considerably smaller than representatives of the same species from Rotuma.‡
* Mousson-Journ. de Conch. xxi. 1873, pp. 102-109.
† Pease—Am. Journ. Conch. iv. 1868, p. 109.
‡ Shipley—Proc. Zool. Soc. 1898, p. 468.
A superficial reader might seize on the fact that many new species are described as new in the following pages, and with a show of reason deduce that so great a proportion of novelties indicate a very peculiar and endemic fauna. This would however be a mistaken impression. Few realise how exceeding rich the fauna of the tropical Pacific is, or how poor our knowledge thereof. Probably, except in New Caledonia, a capable collector would obtain at least one shell new to science in a day's work on any beach in the South Pacific. Fischer's estimate that the Indo-Pacific Province contains five or six thousand marine mollusca,* is certainly below the mark.
For the purpose of comparison the Funafuti fauna must be divided into large conspicuous, and small inconspicuous shells. The distribution already ascertained for conspicuous genera like Cypraea will be paralleled, as knowledge increases, for inconspicuous genera like Caecum. Thus I anticipate the discovery in the western continental islands of every minute species I have' described as new from Funafuti. The range of all the species mentioned is given for the South Pacific as completely as opportunity permitted. A discussion of the data collected is postponed to the concluding pages of this Memoir.
The study of the mollusca of the Pacific is attended with peculiar difficulty. As a result of the superior energy of the British in exploration, commerce and missionary enterprise in the Pacific, the vast majority of the mollusca of this region have, from the time of Captain Cook to the present day, been first examined in London. The writers who have dealt with them, Adams Bros., Hinds, Reeve, the Sowerbys, Smith, Melvill, and others, have treated them uniformly on the model and method of Lamarck; it will be convenient to call this group of authors the "London School." A brilliant exception to the work of British writers is the superb Memoir by Boog Watson on the Gasteropoda collected by the Challenger Expedition.
* Fischer—Man. de Conch. 1887, p. 157.
To descend from generalities to details, it may be pointed out that whilst the foremost British and American writers in all other branches of zoology now use English; whilst the scientific writers of other countries, like Sars and Collett in Norway, Schepman in Holland and various Japanese authors, are adopting English as an international language, on the grounds of its wide currency, wealth and flexibility; yet this conservative London school of Conchologists reject the advantages of their mother tongue and satisfy their humble wants with the poor and awkward medium of Latin.
By some strange unwritten law these Conchologists have invariably maintained a proportion between the size of a shell and its illustration. Thus a large shell, however simple in structure, demanded a large figure; and a small shell, however complex its details, a small drawing. Had this school encountered Pachyderms or Foraminifera, one or both would surely have fallen beyond the focus of their vision.
Though great wealth of anatomical material was profferred them, these writers have ever cast the " nasty things " aside. The fascinating studies of structure, affinities, higher classification, or geographical distribution had no charm for them. Their measure of excellence in Conchological research being apparently the highest score of new species.
But the chief defect of this school is that it has added to the superstructure without strengthening the foundation, and has thus weakened instead of improved the fabric of our knowledge. Upon the distinction of old species depends not only generic and sub-generic classification, but even the reality of new species, which are necessarily contrasted with them. The task of rehabilitating old species, for which these writers have unique facilities, is by them neglected in favour of the easier and more showy work of describing novelties, which could be done at least as well by others.
In illustration, I will cite the following case, one instance of a multitude. Hinds, in 1843,* thus described a new species, Triforis collaris: —"Testa ovata, acuminata; anfractibus duodecimo biseratim granulosis, serie inferiorie paululum maxima, margaritacea, superiore pallide fusca; anfractu ultimo quadriseratim subaequaliter concatenato. Axis 4 lin."
* Hinds—Proc. Zool. Soc, 1843, p. 23.
No one will to-day affirm that so brief an account suffices for the recognition of this species. Consequently there is every probability that it has been, or will be, again named and described to the confusion of science. In so numerous and difficult a group, a description a page long and several detailed figures are barely enough to determine a species in the absence of authentic specimens. It would be supposed that this view only required to be stated for every worker to endorse it, but for sixty-five years British writers have passed over this inadequate account and neglected to repair the fault. So recently as last year, Melvill and Standen in treating of the shells of Lifu, examined and catalogued this species, yet it never occurred to them that a figure and description was more urgently needed for I collaris than for any of the hundred novelties they figured and described.
Great numbers of the species of Adams, Hinds, Smith and others are inadequately represented in literature, and cannot be recognised without an inspection of the type in London. Either therefore no Conchological work should be published except by residents of London, which is an absurd proposition, or these species must be ignored by naturalists.
The local conditions under which the Funafuti mollusca occur may be briefly sketched. The distinction between the marine and terrestrial mollusca, so sharply drawn in temperate zones, fades away in the tropics. At a distance from the sea, in close association with such forms as Stenogyra and Endodonta, occur Littorina, Nerita, Truncatella and Melampus. The outer windward beach, where the surf sweeps the narrow reef platform, is only accessible at intervals when a low tide coincides with calm weather. Here the molluscan assemblage bears the mark of incessant buffeting of waves, all are characterised by powerful muscular feet which adhere to the rock like the sucker foot of the limpet, all have thick shells mostly strengthened by knobs or ridges. In the little rock pools at the foot of the shingle beach, swarm the gaily painted shells of Engina mendicaria, Mitra literata, Conus hebraeus and C. ceylonensis. Beyond, where the surf breaks more heavily, are several species of Sistrum, usually nestled in a rock crevice and more or less concealed by extraneous growth upon their shells. Here also are Purpura armigera and P. hippocastaneum, and on the brink of deep water is Turbo setosus.
It comes as a surprise to a naturalist to find the pelagic fauna scarce in this latitude. Dr. Krämer tells me that he was greatly struck by the poverty of the tropical Pacific in this respect. One Pteropod, one Heteropod, and a fragment of Ianthina were all of this class that came under my notice.
The quiet waters of the lagoon prove a richer field for a collector than the storm swept ledges of the ocean beach. Just at the page 401south end of the main islet of Funafuti, where the lagoon communicates with the ocean, are some clumps of Millepora rising to the surface from about ten or twelve feet. On these is a colony of the giant Vermetus, and built in by coral growth are Magilus and Galeropsis. Near the Millepora were bushes of Plexaura, among whose branches perched Avicula. A sandy flat sheltered behind a long shingle bank yielded at low water Mitra episcopalis, Murex ramosus and Trochus obeliscus.
A mile to the north, where the quiet waters allowed mud to settle, the gregarious Planaxis sulcatus occurred in quantities. Cypraea moneta and C. caput serpentis were here abundant, and to the rocks in the neighbourhood adhered Chama. Nearer the village, at the spot sketched on p. 71, I found as dead shells most of the small species described as new.
A few small reefs in the lagoon opposite the village were excellent collecting grounds. The sandy patches among the coral were inhabited by Strombus luhuanus and S. floridus, and by numerous Cerithidæ, among which the large c. nodulosum was conspicuous. What seemed a brilliantly coloured worm disappeared at a touch with a snap and proved to be the animal of Tridacna elongata seen through the opening of the valves sunk in coral. Loose coral blocks rolled over and split up yielded a harvest; under the block might be Conus rattus, C. lividus or Mitra limbifera, and within it Lithodomus and Area.
In a few hours spent on the leeward islets of the Atoll, I gathered on the beach several large but dead species of Gypraea, Oliva and Conus, which I had not elsewhere encountered. A glimpse of a rich and distinct deep water fauna w.as afforded by a few hauls of the tangles in 80 - 40 fathoms on the western outer slope of the Atoll. Almost everything here collected appears to be new to science.
The sole representative of a fluviatile fauna was a species of Melania which occurred in some abundance in the native wells.
Mr. George Sweet has kindly allowed me to inspect a collection of shells he made on Funafuti in 1897. I have been able in several cases to increase my list by species which he took, but which I had not seen.