CurrsEman.—On the Mollusca of Auckland Harbour, 305 
and Rangitoto—has only an average depth of four or five. Many of the 
bays are very shallow, and extensive mud-banks, often covered with Zostera, 
are daily exposed at low-water. 
The distribution of the Mollusca is well known to be considerably in- 
fluenced by depth, and the sea-bed has, in consequence, been divided by the 
late Professor Edward Forbes and others into four ‘‘ Zones ’”’ or areas, as 
follows :—First, the littoral zone, or the space between the tide-marks ; 
second, the laminarian zone, extending from low-water mark to ten or 
fifteen fathoms ; third, the coralline zone, from fifteen to fifty fathoms ; and 
lastly, the deep sea zone. It is, of course, only the first two of these 
regions that we are concerned with in Auckland Harbour. 
Commencing, then, with the littoral zone, we shall find that no part of 
it is without molluscan inhabitants. When the coast is at all rocky, large 
areas are covered with the common oyster (Ostrea mordax), often associated 
with the mussel (Mytilus smaragdinus.) A peculiar assemblage of species 
is found near high-water mark. Littorina diemenensis is usually in large 
numbers, filling little chinks and crevices, but often also scattered as it 
were broadcast over the surface of the rocks. Another little shell, Adeorbis 
varius, generally accompanies it, but is easily overlooked from its small size. 
A curious minute shell, apparently allied to Leuconia, a sub-genus of 
Melampus, is often found gregarious under stones. Mytilus ater and Nerita 
atrata are also frequently seen near the upward limits of the tide. Further 
down the strand, projecting rocks and overhanging ledges are sprinkled over 
with a variety of small whelks, of which Purpura quoyi, Buccinum testu- 
dineum and B. levigatum are prominent forms. The larger Purpura textiliosa 
is also tolerably common, but P. haustrum appears to be rare. The phyto- 
phagous species are now well represented, especially where the rocks are 
covered with Hormosira or other sea-weeds. Turbo smaragdus, Labio 
zealandicus, L. subrostrata, and Cerithium bicarinata, are all abundant. Two 
or three species of Limpets and a Siphonaria are not uncommon in suitable 
localities. The smaller rock-pools, that are generally fringed with Corallina, 
Jania, and the finer sea-weeds, usually harbour a few species of Rissoa and 
other minute shells; the larger ones, with coarse weeds, are in a great 
measure occupied by Turbo and Cerithiwm. In all, numerous Chitons can 
be found; of these C. pellis-serpentis and €. quoyt principally affect the 
higher pools, while C. longicymbus and C. sulcatus are more common near 
low-water mark. Katharina violacea and Tonicia undulata, both occur 
under stones in the large and deep basins, but are not abundant. The 
finest of all our Chitons, Acanthopleura nobilis, has been found on exposed 
rocks at Rangitoto, but appears to be rare. ‘ 
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