498 Transactions. 
species, unless it be their usually small size, and, of course, their ability to 
retain water within the shell. 
But in dealing with the relations between terrestrial and marine life 
interest naturally centres in those members of the Pulmonata which have 
returned to the littoral belt. The New Zealand species belonging to this 
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while the tide is out. Farnie (Trans. N.Z. Inst., vol. 51, p. 71) records that - 
if left without any water at all they will not live more than a day ; but they 
can live for a month completely immersed in sea-water. The same author, 
in describing the entrance to the lung, states that the lower lip is produced 
. crevices and rock-pools. The anatomy of this species has been studied 
by Cottrell (Trans. N.Z. Inst., vol. 48, p. 582), who describes the respiratory 
orifice as being bounded above by the mantle and below by the body-wall 
differentiated to form a muscular valve. The animal thus has the power. 
of opening aud closing the pulmonary orifice. Siphonaria obliquata 
possesses a gill, so that aeration of the blood is continuous whether the 
animal is submerged or not. If the s ecies is correctly classified as а 
pulmonate, the gill will be a secondary adaptive character. In Gadinia 
la occurs abundantl y between tide-marks. These animals are stated - 
to close their pulmonary orifices while under water and open them when 
exposed to the air. 
to fresh water is gradual: 
water, and sheltered conditions 
