360 
PACIFIC SCIENCE, Vol. IV, October, 1950 
TRAVERSE B - FROM TIDE POLE ACROSS CRAB ISLAND 
20 30 40 50 60 
EHW.S 
MH.W.S 
MH.W.N. 
EiHWN. 
E.H.W.S. 
MH.WS. 
FIH.W.N. 
EiHWN. 
ERLWN, - 
MIWN. - - 
I1L.W.M 
*■10.35 
*•9.28 
CHEI CHAMAESIPHO COLUMNA 
EE3 ELMINIUS MODESTUS 
EED ELMINIUS PLICATUS 
Hill VOLSELLA NEOZELANICUS 
HEE SAXOSTREA GLOME RATA 
^ ENTEROMORPHA ACANTHOPHORA* 
KE2 GELIDIUM CAULACANTHEUM 
ESS CODIUM ADHAERENS 
EZ3 HORMOSIRA BANKSI1 F GRACILIS 
CORALLINA OFFICINALIS 
IHH ENCRUSTING CORALLINES 
m3 CARPOPHYLLUM MASCHALOCARPUM 
VERTICAL SCALE = TWICE HORIZONTAL 
Fig. 4. Traverse B. ( * Found to be Enteronwrpha procera f. minuta. ) 
mapped in late summer ( January-February, 
1948) and therefore include summer aspect 
societies. 
Traverse A (Figs. 1, 3): Across Headland; 
length 101 feet; bearing 116° 20'. 
This traverse was designed to illustrate 
typical zonation of the communities at higher 
levels. It passes from M.L.W.N. 3 to above 
E.H.W.S. and crosses in front of a small cave. 
The angle of dip of the rock, which is to the 
north, is clearly indicated. Dip faces of the 
inclined ledges are exposed to maximum in- 
solation, while strike faces are shaded for 
most of the day. The different aspects show 
differences in the species colonizing the same 
level: for instance, near the end of the trav- 
erse, Gelidium pusillum and V ol sella neo- 
zelanicus flourish on a shaded, vertical strike 
face at the same level as Calothrix scopu- 
3 See Table 1 for full explanation of abbrevia- 
tions used throughout this paper. 
lorum, which usually grows above them. 
In front of the cave mouth (between 80 
and 90 feet) the sand level limits the down- 
ward colonization of Enteromorpha procera f. 
minuta. 
Traverse B (Figs. 1, 4): Crab Island, from 
the tide pole across the longer axis of the 
island; length 122 feet; bearing 136° 30'. 
In Traverse B the relative positions above 
A.H.B. Datum of the more important com- 
munities below E.(L) .H.W.N. can be seen. 
The traverse starts at A.H.B.D., at which level 
Carpophyllum maschalocarpum is flourish- 
ing, and passes upwards successively through 
encrusting corallines, Corallina officinalis, 
Gelidium caulacantheum, oysters, and barna- 
cles. It illustrates the wide extent of both the 
balanoid community at higher levels and of 
Corallina and Hormosira lower down on flat 
surfaces. The steeply ascending rock slope at 
the beginning of the traverse is shaded for 
