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restricted to bottoms and sides of boulders, but we found no ubiquitous
species which strongly preferred tops with the exception of the limpet
Acmaea virginea (Fig. 31).
T A B L E I
Distribution of Commoner Species on Sublittoral Boulders in the
Rapids in J u l y 1948 and J u l y 1950
No obvious preference
Preference for tops
Preference for bottoms
for tops or bottoms
Preference for sheltered bays
Haliclona indistincta
Acanthochitona crinitus
Serpula vermicularis
Adocia cinerea
Bugula jabellata
Mycale rotalis
Escharella varioloaa
Anthopleura ballii
Caryophyllia m i t h i
Cellepora pumicoaa
Membran iporella n itida
~~Preference for intermediate conditions of current
Corynactis viridia
Scrupocellaria reptans
-
Preference for whole main stream
Sertularia operculata
Tubularia bellis
Balanus crenatus
Phimularia setacea
Costazia costazii
Hippothoa hyalina
Umbonula littoralis
Virtually confined to Sill
Sagartia elegans
Patella aspera
Metridium senile
Mytilus edulis
N o obvious preference for current or shelter
Myxilla rosacea
Acmaea virginea
Haliclona limbata
Amphilectia fucorum
Scruparia chelata
Leuconia n,ivea
Halichondria bowerbair ki
Hymedesmia bronsted?
Pomadoceros triqueter
Spirorbis spp.
Balanus balanua
Eseharoides coccineus
Verruca stroemia
Diastopora patina
Crisia eburnea
Schizoin avella spp .
Tubulipora plumosa
Muaculua mrmoratus
Hiatella arcticu
Kellia suborbicularis
Monia s q u a w
Heteranomia squamula
Didemnum maculosum
Lichen opora hispida
* Not on the Sill.