366 The N.Z. Journal of Science and Technology. [Dec. 
• 
Commission, vol. 22, pp. 1-37, 1902) lias described a flourishing fishery 
founded on this species in Japan. To our surprise, Hornell ( Madras Fisheries 
Bull. No. 11, p. 12, 1917)-notes that 0. cucullata is not of economic import¬ 
ance in Madras. In Australia it furnishes abundant supplies to the markets 
of New South Wales and Queensland. During 1917, in New South Wales, 
the 400 people engaged in the industry produced 21,000 bags, worth £53,000. 
O. cucullata is at the extremity of its range in New Zealand, and struggles 
against adverse conditions in these cold seas. It is noteworthy that 
the white mangrove ( Avicennia ) and this rock-oyster disappear together ; 
probably an isothermal zone defines their southern boundary. 
The Auckland oysters throw their spat at long intervals, and, from 
Mr. Bennett’s information, they grow more slowly than in Australia. They 
occur apart, one here, one there, upon the rocks. This dispersal is different 
to the continuous reef which the species forms in warmer seas. Saville 
Kent has photographed such reefs in which the oj^sters are piled on each 
other a foot high and conceal the rocks on which they spread (Saville 
Kent, Great Barrier Beef, pis. xxxix and xl, 1893; id., Naturalist in Aus¬ 
tralia, pi. xliii, 1897). But greater space between individuals means lack 
of competing neighbours, so at Auckland the separate oysters receive a 
larger food-supply, and thus attain an average size larger than those of 
a more genial climate. 
The sedimentary rocks round Auckland are thickly overgrown by a 
small cirriped. The growing oysters spread over the tops of these tiny 
barnacles, and in this way are slightly raised above the surface of the rock. 
From such a base the collector can easily wrench them off unbroken. But 
on the basalt rocks of Bangitoto these minute barnacles do not grow so 
thickly. There the oysters stick so fast to the volcanic rock that a larger 
proportion of them are broken by the collectors. With a cracked shell an 
oyster is apt to die before reaching the market. 
Contrary to Australian experiences, these oysters are said not to thrive 
on mangrove-roots. 
When this oyster occurs near or below the level of low water its aspect 
is so changed as to appear to be another species. Brazier has remarked 
( Proc. Linn. Soc. N.S. Wales (2), ix, p. 561, 1895) that transplantation may 
cause O. cucullata to develop into O. suhtrigona. 
Another kind of oyster,” which Mr. Bennett described but could not 
find for me, was probably Cleidothcierus albidus. Mr. Bennett denounced 
Lepsia haustrum as an oyster-borer, but there are probably other species 
which should be collected and determined. Mr. Bennett had formed the 
opinion that the normal ’tween-tide oyster contributes little to the main¬ 
tenance of the species, and that most of the spawn was shed by a few small 
oysters that grow about low-tide mark. 
The Administration claim that their policy of eliminating private 
management has, resulted in a substantial increase in the output. I 
arrived at the conclusion that where the oysters grow and reproduce as 
vigorously as they do in Australia such a policy would be undesirable, but 
that it may be justified where the general conditions are so unfavourable, 
where spatting is so infrequent and growth so slow as it is at Auckland. 
I would recommend the collection of more exact information. It would 
be of interest to mark specimens, to ascertain their age precisely, to weigh 
and measure them. Records of cultivation, such as the rate of growth 
and exact environment, would be acceptable. Temperature and salinity 
records are also necessary to the proper comprehension of the business. 
