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PACIFIC SCIENCE, Vol. IV, October, 1950 
Lunella smaragda (f) 
Neothais haustrum (o) 
An association dominated by the tubicolous 
polychaetes Hermella spinulosa and V ermilia 
carinifera is characteristic of the shaded 
(strike) faces of ledges on Narrow Neck 
Beach which are adjacent to sand. V ermilia 
nearly always occurs above Hermella, al- 
though the two species occasionally intermix. 
Hermella appears to be more tolerant of 
mud. At St. Leonard’s Point it reaches maxi- 
mum development, forming sandy hum- 
mocks which are easily eroded by wave action 
and which provide a place of refuge for 
numerous small crabs. V ermilia carinifera 
consists of calcareous tubes attached length- 
wise to the substrate. The animal occupies 
only the opening of the tube and protrudes 
when lying in a small pool, but if the shell 
is exposed to air it retreats within the tube, 
which it closes with a shelly operculum. 
Subordinate species include Codium ad- 
haerens, forming compact, radiating cushions 
on either sandy or calcareous worm tubes 
(Fig. 10), together with the usual barnacles 
and molluscs, including chitons, limpets, Lu- 
nella smaragda, and occasionally Neothais 
haustrum. 
Lower Mixed Algal Formation 
3. Corallina — Hormosira Association 
(Fig. 11) 
Vertical range: 3. 7-0.8 feet. Between 
E.(H) .L.W.N. and M.— E. L.W.S. 
Exposure: 22.2-0.5 per cent. 
Corallina officinalis (d) 
Colpomenia sinuosa (a) 
Codium adhaerens (f) 
Caulacanthus spinellus (f) 
Laurencia hotrychioides (f) (summer) 
Laurencia thyrsifera (o) 
Diet y ota ocellata ( o ) 
Derbesia novae-zelandiae (r) 
Poly sip honia sp. (r) 
Chamaesipho columna (f) 
Tethya fssurata (f) 
Hormosira banksii f. gracilis (d) 
Leathesia difformis (a) 
Gelidium caulacantheum (f) 
Enteromorpha procera f. novae- 
zelandiae (f) 
Splachnidium rugosum (f) (summer) 
Microdictyon mutabilis (o) 
Symphyocladia marchantioides (o) 
Dasya subtilis (r) 
Lophurella caespitosa (r) 
Elminius modestus (f) 
Lunella smaragda (f) 
Below the level of low water neap tides, 
there is an abrupt change in type of com- 
munity: animals become of secondary eco- 
logical importance, and algae of one kind or 
another are physiognomic. There is also a 
notable increase in the number of species 
and, in general, a decrease in numbers of in- 
dividuals. In the relatively sheltered waters 
of the Hauraki Gulf the Corallina — Hormo- 
sira association is the most widely distributed 
algal community in the inter-tidal region. 
Dull reddish-brown in gross appearance, it 
covers all the available space on flat or gently 
inclined rocks between low water neap and 
low water spring tide levels. Although Hor- 
mosira banksii often dominates a separate 
consociation in other localities (e.g., on Taka- 
puna Reef), at Narrow Neck it is seldom 
found growing apart from Corallina. The 
regular line delimiting C. officinalis from the 
balanoid association above (Fig. 11) is broken 
here and there by upward penetration of 
the Corallina ■ — Hormosira association along 
cracks in the rock which serve as drainage 
channels. 
Hormosira seems unable to establish itself 
in large numbers on vertical or steep slopes. 
Towards the lower limit of the association it 
gradually drops out, and Corallina assumes 
dominance. The latter forms a short turf of 
tufted plants, apparently comparable to the 
algal turf described by Stephenson (1939, 
1944) for South Africa. 
