Inter-tidal Zonation — CARNAHAN 
37 
Littorinoid Formation 
This formation is that of the uppermost 
littoral and lower supralittoraL Its communi- 
ties may reach upwards to the highest levels 
ever submerged. 
There is one principal association on rock, 
although several fasciations occur where there 
is sediment. The patchy nature of the com- 
munities of the upper littoral differs from the 
usual "closed” nature of littoral communities 
on Rangitoto. 
1. Melarhaphe-Li china association 
Melarhaphe oliveri d 
Lichina pygmaea d 
Bostrychia mixta f 
Ralfsia sp. f 
Flacoma vesiculosa f 
Lichina has a narrower vertical range than 
that of Melarhaphe, its upper limit being at 
M.H.W.S.T. Its lower limit is that of Melar- 
haphe, in the vicinity of M.H.W.N.T. 
Several subordinate species occur, scattered 
within similar limits to those of Lichina, e.g., 
turfs of Bostrychia mixta are frequent, and 
there are also an encrusting Ralfsia sp. and 
small colonies of Flacoma vesiculosa. 
2. Caloglossa-Catenella fasciation 
Caloglossa leprieurii d 
Catenella nipae d 
Bostrychia mixta f 
Hildenbrandia prototypus o 
This community occurs within the levels 
of the Melarhaphe -Lichina association, where 
there is some sediment. It is found particu- 
larly in crevices and other shaded places, 
where Hildenbrandia prototypus also takes part 
in the community. Caloglossa and Catenella are 
also found, together with Rhizoclonium hook- 
eri, on mangrove pneumatophores (see 
"Avicennia officinalis consocies”). 
3. Myxophycean fasciations 
Several Myxophycean communities are as- 
sociated with varying degrees of sedimenta- 
tion in the high tidal levels. These are domi- 
nated by one or more of the following species: 
Calothrix scopulorum, Lyngbya semiplena, Phor- 
midium ambiguum, and Oscillatoria nigroviridis. 
Barnacle Formation 
The communities within this formation oc- 
cupy the large mid-tidal portion of the littoral 
(M.H.W.N.T.-M.L.W.N.T.). The two prin- 
cipal associations are characterised by the co- 
dominance of the barnacle Chamaesipho 
columna. 
4. Chamaesipho-Apophlaea association 
Chamaesipho columna d 
Apophlaea sinclairii d 
Gelidium pusillum f 
This association occupies the upper por- 
tion of the mid- tidal levels. The lower limits 
of both dominants, as individuals, lie well 
below the lower limit of the association, but 
Apophlaea is dominant only within the limits 
of the association. The vertical range of 
Gelidium pusillum, a scattered, turf-like species, 
lies across that of the association. 
5. Chamaesipho-Saxostrea association 
(Fig. 2) 
Chamaesipho columna d 
Saxostrea glomerata d 
Flminius plicatus f 
Fig. 2. Zonation on sloping scoria shore. Chamae- 
sipho-Saxostrea association (white), Corallina-Hormosira 
association (grey), Carpophyllum-Ecklonia association 
(dark; bottom of slope and foreground). 
