OrrvER.— Marine Littoral Plant and Animal Communities. 529 
mark near the outer extremity of this reef.. Two such communities are 
very conspicuous : one is that of Vermilia carinifera, quite the most remark- 
able of its kind I have seen; the other is an association in which the tuni- 
cate Cynthia is the dominant form.. This species occupies a belt of rocks 
extending from low-water mark at spring tides to nearly 1 m. in vertical 
height above. It occurs usually in clusters, some twenty or thirty being 
united, and attached to the rock or to an adjoining cluster at five or six 
places З 
. (Plate 42, fig. 3.) Тһе tunicate does not completely cover the rock, but 
rocks are usually more or less bare. The fact that the individuals in a 
cluster. сап be separated, though with difficulty, shows that the mode of 
forming clusters is simply by the young settling on the outside of the tests 
of older individuals and growing there. Many young can be found in 
such positions. The tests, where touching, are joined together very firmly 
by their stringy and glutinous exteriors, and thus compact clusters are 
formed. Another larger species of tunicate occurs singly along the lower 
Frequently embedded in the masses of Cynthia occur little colonies 
of Musculus impactus, each spinning round its shell a nest resembling a 
n rocks among the tunicates are many animals and plants. The 
globose sponge Tethya, and an encrusting bright-orange species, are com- 
m rallina officinalis is abundant, and collects a lot of mud. 1t 
small Elminius. Ostrea corrugata up to Т ст. in length occurs singly or 
in small clusters. Patiriella regularis is common, and apparently always 
of a reddish-brown colour. Mytilus canaliculatus occurs singly in crevices. 
The shells are usually almost covered with Crepidula crepidula, and er 
sionally also some Calyptraea novae-zealandiae, Amaurochiton glaucus, an 
Ischnochiton maorianus. 
The under-side of stones is equally as rich as the upper surface. Near 
the mud-line are Ischnochiton maorianus and dopleurus iredalei ; but 
where the water circulates freely, though = c not fall dus ce: 
are Cynthia, but no algae, and numerous gasteropods, sponges, 
varie de, экин жы crabs, pelecypods, Flabelligera lingulata, Nereis 
amblyodonta, and other worms of various kinds. (Plate 47, fig. 1. 
Corella Association. 
here 
Bay of Islands.—On the rocky coast of Long Beach, under stones w 
no light Бетен there is often a rich collection of qr ccn - 
these may be merely sheltering during the recess of the tide ; : n xi 
the contrary, belong to species always found attached to the under-side o 
