Inter-tidal Ecology at Narrow Neck Reef — Dellow 
365 
local environment. During a hot summer 
afternoon, when the tide is low, it will mi- 
grate to a shallow pool beneath an overhang- 
ing ledge, while just after being uncovered 
by the tide it will present a more uniformly 
scattered pattern of distribution. 
Balanoid Formation 
2. Enteromorpha — Gelidium — Volsella 
(Modiolus) Association 
Vertical range: 10.8-6.3 feet. Between 
M.H.W.M. and M.S.L. 
Exposure: 94.7-58 per cent. 
Enteromorpha procera f. minuta (d) 
Volsella ( Modiolus ) neozelanicus (d) 
Chamaesipho columna (a) 
Onchidella patelloides (o) 
Gelidium pusillum (d) 
Ralfsia verrucosa (a) 
Centroceras clavulatum (f) 
Elminius modestus (f) 
Although sometimes epiphytic on Geli- 
dium pusillum, Enteromorpha procera f. mi- 
nuta more often dominates in exposed situa- 
tions immediately below the Calothrix — 
Melaraphe association. The small mussel 
Volsella ( Modiolus ) neozelanicus is usually 
entangled within the dense cushions formed 
by G. pusillum. Striking evidence of the re- 
actions of these species to exposure and shel- 
ter is seen on the rock face south of the 
Headland cave (Traverse A, Fig. 3). Where 
the slope is vertical, with a curve that faces 
the incoming tide, Enteromorpha dominates. 
Where the rock is shaded or overhanging, 
the dominants are Volsella and Gelidium. 
a. Enteromorpha Consociation 
E. procera f. minuta fluctuates seasonally 
in abundance. Although present all the year 
round, it reaches maximum extent in autumn 
and winter, with a secondary growth period 
in spring. During the hottest summer months 
(January and February) the Enteromorpha 
community on wharf piles in the Auckland 
Fig. 8. Volsella neozelanicus consociation on a flat ledge between Narrow Neck and St. Leonard’s 
Point. 
