PART I 



MOLLUSCA 



BY CHARLES HEDLEY 



(Prepared by permission of the Trustees of the Australian Museum, Sydney) 



(With Plate I.) 



EDITORIAL NOTE. Mr. Hedley has asked me to preface his report with field notes on the species. The 

 Mollusca were collected in two localities, within a short distance of one another at Cape Royds, yet of 

 totally difl'erent character. The "Bay" is a very small shallow inlet, lying to the east of our camp, 

 between Gape Royds and Cape Barne. It appears to be little affected by currents, or even by storms, for 

 the ice forms early there and stays late. Wherever it has been examined at depths of more than two 

 fathoms, the bottom resembles the bed of a lake in being covered with a fine tenacious black silt. In 

 consequence of the early formation of the winter ice in the Bay we were able to dredge there as early as 

 April, and frequently afterwards till July. Then this dredging-ground was lost, and no more work was 

 done in the Bay till February, when the ice had gone out of part of the Bay. The Bay is only free from 

 ice for a few weeks in summer, perhaps in cold seasons not at all. The dredging was done at depths of 

 between seven and twenty fathoms. 



The " Sound " is a situation of very different character. The part where most of the dredging was done 

 is at the mouth of the Bay, where the bottom begins to slope down into deeper water. A strong current 

 prevails there, as indicated by Brocklehurst's Current Indicator, and by the effect on our dredging lines. 

 The bottom is free from mud, even in shallow water close by the cliffs of Cape Royds. At a depth of less 

 than twenty-five fathoms there are many pebbles and boulders of keny te and other rocks. At greater depths 

 no pebbles are found, the dredge bringing up only living or dead organisms, which apparently grow so 

 densely crowded together that the dredge never touches the bed of the sea, of whatever materials composed. 



The molluscan fauna of these two localities differs greatly. In the Bay the dominant forms are 

 Neobuccinum, Anatina, Pecten, and Yoldia. The delicate Trophon is not rare, and there are many small 

 and even microscopic molluscs, both Gastropods and Lamellibranchs. 



Neobuccinum eatoni appears to surpass all the other large species in abundance, but this may be due to 

 its activity and voracity. It comes readily to any bait which is put down for even a short time. No trap 

 or dredge is needed to get them. They hold tight on to the bait and come up with it. They must have 

 keen senses, of whatever sort, as the crowds which sometimes covered the bait must have collected from 

 some little distance around. The shells of Pecten colbecki are very abundant, but the animal was rarely found 

 alive. The first living example was got on June 17, between seven and twelve fathoms. On account of the 

 delicacy of its valves it was removed from the bucket and placed on the ice for safety. The temperature 

 was low, and it showed its disapproval of its first experience of a temperature ( - 10 F.) forty degrees below 

 that to which it was accustomed by snapping angrily for some time. When replaced in the bucket and 

 conveyed to the house it seemed none the worse, and again snapped when exposed to the air. It lived for 

 many hours, under the influence of a weak narcotic (Eucaine), thus showing a tenacity of life unusual 

 among Antarctic marine animals, and unexpected in this delicate Pecten. A very small specimen was 

 dredged on a stony bottom, at a depth of only two fathoms, close to the shore. 



The shells of Anatina are very abundant and of large size, but only very small examples were got alive. 

 BEIT. ANTARCT. EXPED. 1007-9. VOL II. PART 1, ISSUED APRIL 1911 A 



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