58 
The Queensland Naturalist. 
VoL. 2 
their greatest development here. The Chthamalus horizon 
is, perhaps, to be regarded as the lowest portion of the 
Melamphe zone, using the name then in a wider sense. 
The commonest species is M. iinifasciata [M. mauritiana) . 
Another member of the fauna is M. melanacme, while Cellana 
Bemhicium, Siphonaria and Tetraclita purptirascens may 
invade it. Young specimens of Tectarius pyramidalis also 
occur here. 
Melaraphe infans suh-zone.—lihSs includes the rather 
fiat expanses of rock, especially on Caloundra Head, which 
lie at about the same level as Chthamalus, and extend inwards 
towards the shore. They are hot and dry during part of 
the day, and sometimes are encrusted with salt under the 
influence of a hot sun. There is no conspicuous animal or 
plant life, but on careful examination one sees immense 
members of tiny dark grey Mollusca, Melaraphe infans, and 
M. acntispira, huddled together and resembling fine coal 
grit caught in the irregulanties of the rock surface. Some- 
times a slippery filamentous Entcromorpha occurs here. 
This sub-zone is a part of the Melaraphe zone in its 
wide sense. 
E. Tectarius 2one. — This horizon is characterised by the 
presence of only one marine organism typically, vi-:., Tectarins 
pyramidalis, a mollusc occupying a very wide zone, varying 
in width in different situations, according to the height to 
which spray is thrown at high spring tides. I have seen it 
occasionally at a higher level than the grass and lichens 
which mark the downmost limit of terrestrial vegetation on 
the ocean reef beach. Tectarius is a member of the 
Littorinidas. We have noticed that the succession of species 
of the family here is just the same as in Sydney district 
That with the lowest range is Bemhicium melanostoma, which 
extends upwards into the Melaraphe zone ; then come in 
ascending order Melaraphe acutispira, M. infans, M. nielan- 
acme, M. unifasciaia and Tectarius pyramidalis. In the 
Hribie Passage Mel. scahra may reach even higher, being 
found on the stems and leaves of mangroves. Here the 
marine and land flora are not widely separated. 
The Siphonaria region is very restricted, the term being 
used to designate those areas where Siphonar'ia scahra is the 
dominant organism. This is a common species, and extends 
from the Sargassum zone to the Melaraphe horizon. Where 
the rocks are fairly smooth, and slope towards the sea, affording 
little protection against the sweeping movement of the 
waves, few other organisms are present. Here the limpet 
snail S. scahra occurs in numbers as a low cone, with a few 
radiating ridges on its shell, and a distinct siphon on its righl 
side. Irregularities of the surface may afford more shelter, and 
