Art. XXXVI.—Notes on a Remarkable Collection of Marine Animals lately found on the New Brighton Beach, near Christchurch, New Zealand.
[Read before the Philosophical Institute of Canterbury, 1st September, 1897.]
The New Brighton Beach does not usually afford a very rich harvest to the collector of marine animals. Formed by a gently-sloping expanse of sand, rising inland into low dunes, it is entirely devoid of those rock-pools which, on other parts of the coast, afford such a happy hunting-ground to the naturalist.
The littoral fauna of New Brighton consists of animals which for the most part live buried in the sand, such, for example, as the well-known pipi (Mesodesma spissa), which forms enormous beds in certain parts of the beach, recognised by the innumerable small holes in the sand, through which, when the beds are covered by the advancing tide, the bivalves protrude their long extensile siphons, in order to take the sea-water into the mantle-chamber for respiratory and nutritive purposes. Nearer the sea, just about low-water mark, lives that remarkable sea-urchin Arachnoides placenta, whose delicate flat shell, though common enough, is so rarely found entire among the déAbris thrown up at high-water mark; and it is to this same zone that we must probably assign the common but handsome bivalves Dosinia australis and Mactra œquilatera.
Further out again, and probably at a depth of several fathoms, there must be a great sandbank inhabited by a very rich animal population. As a rule this bank appears to be undisturbed by tides and currents, and its inhabitants are rarely seen thrown up on the shore. Occasionally, however, dead valves of Glycymeris (Panopea) and Zenatia are met with on the beach, and one or two specimens of the pink scaly Holothurian, lately described by me under the name Colochirus ocnoides, have also been found from time to time. In July, 1896, also, immense numbers of young specimens of the even more strange-looking Holothurian long since named by Captain Hutton Caudina coriacea were met with on the beach, but they were all young, and probably came from a bank in shallower water than that frequented by the adults.
A few days ago, on the 24th August, I was informed by Mr. Sinclair that a large quantity of shellfish had been thrown up on the New Brighton Beach, and my curiosity was keenly aroused by the sight of fresh specimens of Glycymeris (Panopea) and Zenatia, with the animal in a perfect state of preservation, which he kindly brought for my inspection. I immediately went down to New Brighton, and was rewarded by a sight which was truly astonishing. About half a mile south of the pier, between tide-marks, lay an immense bank of shellfish, intermingled with other animals. I believe I am not exaggerating when I say that there were many tons of animals there. So numerous were they that even the voracious gulls, which usually destroy everything almost as soon as it is thrown up on the beach, had been able to make very little impression upon the great mass of animal food thus unexpectedly provided for them. I am told that a similar bank of shellfish was lying nearer the Heathcote estuary, but I had no time to visit this. Of course, there were also quantities of the animals scattered along the shore.
The bank which I visited was made up principally of Zenatia acinaces (=deshayesi), a bivalve hitherto considered rare, at any rate on this part of the coast. It evidently lives buried in the sand, and it has a long single siphon containing the united exhalant and inhalant tubes, and a well-developed foot of a beautiful pink colour, which is doubtless used for boring its way into the sand. Much less common, but still abundant, was Vanganella taylori, also in a living condition, a large bivalve of a genus peculiar to New Zealand, of which the animal has been almost, if not quite, unknown. It also has a well-developed foot, but of a white colour, and a well-developed siphon containing the united exhalant and inhalant tubes. A much more remarkable bivalve is Glycymeris (Panopea) zealandica, with an enormous siphon, which must be fully 8 in. or 9 in. long in the extended condition, and an aborted foot, which can probably be protruded through a small aperture left between the soldered mantle-lobes in front, and may still be used as a boring-organ. It must have required a powerful disturbance of the sea to dig out and cast on shore this animal, buried probably to a depth of about 1 ft. in the sand. It was not nearly as common as Zenatia, but many specimens were found.
The most beautiful of the shellfish was the delicate unequal-valved form generally known under the name of Anatina angasi, a species which I believe has hitherto rarely been found so far south, but which was thrown up in large numbers on this occasion. These living specimens showed that the animal possesses separate inhalant and exhalant siphons, a fact which Mr. Suter tells me will probably necessitate the removal of the species from the genus Anatina altogether. The other bivalves met with in the fresh condition were Tellina alba, Mactra discors, Dosinia australis, Venus yatei, and Solenomya parkinsoni, the last named, which is extremely rare, being remarkable for its peculiar sucker-like foot. Lucina dentata was brought to me with the animal in a few days later, and I believe a good many specimens were found.
Mr. J. B. Mayne also obtained a fine living specimen of Pinna zealandica a few days afterwards from the same beach. It is probable, however, that the Pinna, which is not infrequently met with on the beach, came from a different locality from the majority of the Lamellibranchs mentioned; it is found incrusted with seaweed and Polyzoa, and probably comes from some muddy shore in the neighbourhood of Lyttelton Harbour.
In addition to the lamellibranchiate molluscs, which constituted by far the greater part of the spoil, I must mention the following animals found amongst them: Pinnotheres
pisum, a small crab which I have found living as a commensal in Mytilus latus, Vanganella taylori, and Pinna zealandica, and which Mr. Suter tells me also occurs in Mactra discors and Mactra equilatera, was very abundant.
The remarkable Holothurian Caudina coriacea was found in enormous numbers, and the specimens were nearly all adult, while on a previous occasion, as already mentioned, large numbers of young specimens were thrown up, and no adults. The American Caudina arenata is known to bury itself in the sand with only the tip of the tail projecting, and doubtless the same is true of our species, so that only a considerable disturbance of the sea-bed could cause it to be thrown on shore in such quantities.
Colochirus ocnoides, a curious scaly Holothurian, resembling a pink worm, which I have lately described for the first time in the “Proceedings of the Linnean Society of London,” and which has hitherto been known only from a very few specimens, was found in thousands. Probably I should be correct in saying that there were millions of this animal lying on the beach; they lay in heaps, and might have been collected with a shovel.
Echinocardium australe, a widely-distributed heart-urchin, rarely found at New Brighton, was represented by a few dead specimens.
I reserve for the end the most interesting find of all, a very large Gephyrean worm, a new species of Echiurus, which I propose to describe under the name Echiurus novœ-zealandiœ. Of this I was fortunate enough to find three specimens in the short space of time at my disposal, and Mr. Alfred Cockayne, who afterwards kindly searched for it at my request, found four more, three of which are now in the possession of the Canterbury Museum. This animal in life resembles an elongated cylindrical bag or bolster. It may be more than 8 in. long, with a thickness in the middle of about 1 in. when extended. When contracted it looks like a short thick sausage, becoming loose and baggy when badly preserved. The colour in life is dark purplish-red, and the body cavity is filled with a rather thick dark-red liquid resembling blood and containing numerous corpuscles. The skin is smooth. Anteriorly the body is produced into a very short proboscis, resembling a stand-up collar, with a slit down the front. At the base of the collar, below the slit, are two horny hooks, and a single ring of similar hooks surrounds the body at the hinder end, a short way in front of the terminal anus. The animal resembles a Japanese species, Echiurus unicinctus, which is used by the Japanese fishermen for bait, but it differs in its much larger size, its smooth integument, and probably also in some details of internal anatomy. It forms an extremely in-
teresting addition to the New Zealand marine fauna. Mr. H. B. Kirk informs me that he has in former years seen this animal thrown up in large numbers on the beach at Petone, near Wellington. My own attention was first attracted to it by a specimen in the Wellington Museum, of which the history was unknown, since when I have been on the look-out for it, and it afforded me no little satisfaction to rediscover it in the living condition at New Brighton.
Pelagic animals, such as Physalia, Spirula, and Phronima, which are sometimes thrown up on the New Brighton Beach,* the first named often in large numbers, were on this occasion remarkable for their absence, the only indications of pelagic animals which I noticed being a few lumps of jelly, apparently belonging to some medusa.
It was surprising to notice how quickly the vast heaps of shellfish disappeared, buried in the sand or swept out to sea again; in a fortnight from the time when they were cast on shore scarcely a trace of them was visible, and the beach had resumed its ordinary uninteresting aspect.
The cause of the unusual and, so far as I know, unprecedented phenomenon recorded in this short notice is not very easy to determine. Mr. R. M. Laing, M.A., who has had much experience in collecting on this coast, tells me—and what he says harmonizes very well with my own observations—that there are two well-marked currents in the sea off New Brighton—the one more inland coming from the mouth of the Waimakariri River, trending south along the shore, and bringing with it enormous quantities of drift-wood when the river is in flood; the other, a more important current, trending northwards for a long distance up the coast. It is probably this latter which, in heavy weather, brings to the beach, from the rocky coast of Banks Peninsula and the mouth of Lyttelton Harbour, the vast quantities of the giant seaweeds Macrocystis and D'Urvillea, amongst whose roots numerous Polyzoa, Chitons, and other small animals are to be found, and also the remarkable stalked Ascidian Boltenia, one of the commonest animals found on the beach, and the handsome Pinna already referred to. It is possible that, as Mr. Laing further suggested to me, the two currents may meet and form a vortex. I imagine that under certain conditions this vortex may become so powerful as to churn up the sand to a considerable depth, bringing to light its buried inhabitants, which are then cast on the shore by the heavy tides. Something of this kind seems to have happened lately, for the majority of the animals cast up were certainly sand-dwelling forms. They probably came from some locality directly opposite the
[Footnote] * In the case of Spirula only empty shells, as usual, are found.
beach, and they reveal a hitherto unsuspected wealth of animal life which may be of great importance as a food-supply for marine fishes, which are very abundant along this coast. Callorhynchus antarcticus must have a breeding-ground somewhere close by, for the egg-cases of this fish are thrown up in enormous numbers on the New Brighton Beach.
Mr. C. O. Lillie, of the Canterbury Agricultural College, has kindly supplied me with the appended information as to the wind during the ten days prior to the 24th August, as recorded at Lincoln, distant about sixteen miles inland from New Brighton. The great mass of animals was certainly thrown up on the shore a few days before the 24th. I have little information as to the exact time of their appearance, but I am informed by one of my students that they had begun to appear on the 21st, though not in any quantity. It will be seen from Mr. Lillie's report that there was an unusually strong north-east wind on the 17th and 18th, and to this I am inclined to attribute the disturbance. The normal currents may have been diverted temporarily so as to cut into a sandbank usually undisturbed; or a vortex may, as already suggested, have been produced, possibly assisted by the sudden change of wind from north-east to south-west.
|Number of Miles of Wind for Previous Twentyfour Hours.||Direction at 9.30 a.m.|
Too much reliance should not be placed on these records—in fact, regard them as rather qualitative than quantitative. A high wind for twenty-four hours gives a reading between 300 and 350 miles. The reading of 354 miles on the 18th shows that there was a strong wind on the 17th–18th.
C. O. Lillie,
Mr. Henry Suter has kindly supplied me with the following list of Mollusca which he has found on the New Brighton Beach at various times, including those recently thrown up:—
Plaxiphora coelata, Reeve.
" ovata, Hutt.
Chiton sinclairi, Gray.
Onithochiton undulatus, Q. and G.
Patella stellifera, Gmel.
Haliotis iris, Martyn.
" virginea, Chemn.
Emarginula striatula, Q. and G.
Astralium cooki, Chemn.
Calyptræa calyptræformis, L.
Struthiolaria papulosa, Mart.
Siphonalia nodosa, Mart.
Trophon ambiguus, Phil.
Scaphella pacifica, Lam.
Ancilla australis, Sow.
æolis plicata, Hutt.
Amphibola avellana, Chemn.
Siphonaria zealandica, Q. and G.
Solenomya parkinsoni, Smith.
Mytilus magellanicus, Chemn.
" latus, Chemn.
Pinna zealandica, Gray.
Ostrea reniformis, Sow.
Chlamys zealandica, Gray.
Lucina dentata, Wood.
Tellina alba, Q. and G.
" disculus, Desh.
Mactra discors, Gray.
Mactra æquilatera, Desh.
Vanganella taylori, Gray.
Zenatia acinaces, Q. and G. (= Z. deshayesi, Reeve).
Mesodesma novæ - zealandiæ, Chemn.
Mesodesma spissa, Reeve.
Dosinia australis, Gray.
" subrosea, Gray.
Venus yatei, Gray.
" stutchburyi, Gray.
" costata, Q. and G.
Petricola siliqua, Desh.
Psammobia lineolata, Gray.
Solenotellina nitida, Gray.
" spenceri, Hutt. (M.S.).
Glycymeris zealandica, Q. and G.
Saxicava arctica, Sow.
Bontæa (?) angasi, C. and F. (Anatina angasi, Auct.)
Spirula peronii, Lam.