OrivER.— Marine Littoral Plant and. Animal Communities, 527 
include Chamaesipho columna, Elminius plicatus, Cellana ornata, C. denti- 
culata, Siphonaria obliquata, S. zealandica, Risellopsis varia, and Melaraphe 
cincta ; also Sypharochiton pellisserpentis in crevices, and Melaraphe uni- 
jasciata in the upper portion of the association. 
Small-olive-red-algae Subformation. 
Two associations of small close-growing algae are included. The 
Bostrychia association occurs high up in the intertidal belt, where it occupies 
patches of various sizes on the rocks. It always harbours small pelecypods 
and gasteropods.  Bostrychia arbuscula has an outside layer of tissue with 
thick-walled polygonal cells. Under drying conditions of the atmosphere 
it shows signs of wilting, the tips of the filiform thallus-segments curling 
up. This association is confined to the south of New Zealand. I have not 
observed it farther north than Shag Point, Otago. 
Caulacanthus spinellus is more widely distributed, and is the northern 
representative of the small-olive-red-algae subformation. It occupies patches 
of rock above the belt of Ostrea cucullata, usually affecting shady places. 
It is of low, dense growth, and harbours small pelecypods, worms, 
other animals. 
Bostrychia Association. 
Stewart Island.—The upper belt of intertidal rocks at Golden Bay is 
characterized by an association in which Bostrychia arbuscula takes the 
chief part. This species covers patches of the rock to a height of about 
О mm., growing in little tufts. The belt it occupies would be exposed to 
the atmosphere for more than twelve hours daily. The tips of the thalli 
are filiform, and curl up in the sunshine and wind. At the base of this 
alga is found abundantly the small pelecypod Lasaea miliaris and small 
amphipods. Also characteristic of this association are Melaraphe cincta, 
some small Elminius: modestus, Risellopsis varia, Notoacmea parviconowea, 
and Modiolus pulex. Under stones one finds Atalacmea unguis- almae, 
Leuconopsis obsoleta, and small Monodonta coracina. — 
t. Clair.—On rocks near high-water mark there is a well-marked belt 
composed of a close growth, 1-2 cm. tall, of Bostrychia arbuscula. The 
left by the tide, though it may 
day. Bostrychia arbuscula forms large 
о 
occurring in this association are the young of Lepsiella scobina and 
Siphonaria zealandica. : 
Shag Point.—Here this association is developed in patches above pe 
tide mark. There is a fairly dense growth of Bostrychia arbuscula, 1-1- a 
tall. The bases of the thalli are flat, give off branches on each side, an 
at the ends clusters of filaments 0-1 mm. in diameter. On the p 
are small specimens of Chamaesipho columna and Modiolus ie i he 
alga grows on these as well as on the rock. Among the bases of Dos rychia 
are crowds of Lasaea miliaris, 2-3 mm. in length. These shells — 
young up to 0-6 mm. long. Young shells of Melaraphe cincta up “4 mm. 
are abundant, all shells from 2 mm. to 3 mm. and longer having the spire 
eroded, The young of Risellopsis varia are not common, but occur up 
