MOLLUSCA. HEDLEY. 
17 
Little information has reached me on the ecological aspect of the beaches at 
Macquarie Island. The range of the tide and temperature of the water will probably 
be discussed in another section of these reports. 
In the narrative of the Expedition (II., p. 241) it is noted that “ Very few stretches 
of what may be called £ beach ’ occur on the island ; the foreshores consisting for the 
most part of huge water-worn boulders or loose gravel and shingle. After a storm 
the sea piles up hundreds of tons of kelp on the shore, and for several days tangled 
masses like small islands drift about.” The kelp growing on the rocks, as exposed at 
low tide, is shown on the plate facing p. 44 of “ The Home of the Blizzard.” 
Now that Macquarie Island has been so fully examined, the Crozets probably remain 
the least zoologically known of the Subantarctic islands. 
The systematic account of the species is as follows :— 
Class PELECYPODA. 
Pronucula mesembrina sp. nov. 
(Plate I., figs. 1 and 2.) 
Shell small, oblique, triangularly ovate, moderately inflated, inequilateral, clothed 
with a tough persistent buff epidermis. Beak prominent, set at about three-quarters 
of the length. Upper and central portion of the valve with fine, irregular, concentric 
growth lines, the lower half with about 50 delicate and crowded radial riblets. Interior 
brilliantly nacreous, with a silver lustre ; the radials show an imprint, and denticulate 
the inner margin of the valve. Muscle scars not visible. Hinge with the chondrophore 
apart from the teeth, of which there are five tubercles and sockets on the posterior 
side and three on the anterior. 
Length, 2-2 ; height, l-7mm. 
The species is represented by a single left valve, broken at the anterior edge. This 
was fast to the web of a worm tube, taken January 19th, 1912, at Aerial Cove, Macquarie 
Island, by Mr. H. Hamilton. This is the fourth member of its genus, the others being 
P. decorosa Hedley, from New South Wales; P. hedleyi Pritchard and Gatliff, from 
Tasmania ; and P. kermadecensis Oliver, from the Ivermadecs. 
Leda oblonga Pelseneer. 
Leda oblonga Pelseneer, Zool. “ Belgica,” Moll., 1903, p. 23. pi. vi., figs. 79, 80. 
The type of this species came from the opposite end of Antarctica ; but one entire 
shell and one single valve agree precisely with Pelseneer’s figures and description, except 
that Mawson’s specimens are 5mm. long, and the “ Belgica’s ” only 4mm. These were 
dredged January 31st, 1914, in 358 fathoms ooze, off the Shackleton Ice-shelf in South 
Lat. 64° 44' and East Long. 97° 28'. 
Vol. iv., Part 1—c 
