240 THOMAS C. BROWN 
while to compare the following quotations concerning modern 
occurrences. 
There is also a small vegetable group, that furnishes a considerable quota 
toward the composition of the characteristic coral-rock. It is that of the pecu- 
liar seaweeds or lower algae known as Corallines or Nullipores. They are 
distinguished by the incrustment of their tissues with carbonate of lime, to 
such density that their vegetable nature is completely disguised; and, except- 
ing for the absence of the characteristic pores, they might in many instances 
be mistaken for the coralla of the hydroid coral Millepora.... . In the 
deeper rock pools, and on the sea bottom generally, in the neighborhood of the 
reefs, another generic form, Halimeda, belonging to the same nullipore tribe, 
is locally abundant. This type forms erect, branching tufts, often several 
inches in length, of which the branchlets are composed of flattened, irregularly 
polygonal, or more or less fan-shaped, calcareous disks, strung together, as 
it were, in a moniliform or chainlike order. While growing, this nullipore is 
a brilliant grass-green, but it bleaches, when dead, to a pure white. The 
bleached discoidal segments of its disintegrated fronds often occur in great 
abundance among the mixed calcareous components of reef-rocks and coral 
sand.t 
In describing the reefs of the Bahamas Agassiz says: 
Nullipores are most abundant on the summit of the reef, growing upon 
the smaller fragments of broken corals, which they also often cement together, 
when they are forced inward into the deeper part of the lagoon, where the 
cemented masses frequently form heads of considerable size. Longitudinal 
and cross-sections of the lagoon show that its bottom is uniformly covered 
with coarse sand and broken shell material, or fine sand, according to the dis- 
tance from the action of the breakers. Upon this looser material algae and 
corallines thrive and grow abundantly, generally in large patches. 
Immense masses of nullipores and corallines grow on the shallowest flats, 
on the tops of the branches of madrepores which have died from exposure 
to the air, either because they have grown up to the surface and so have become 
exposed by extreme low tides, or because strong winds have blown the water 
from the flats.3 
Not only are the Nullipores very abundant in many of the 
modern coral reefs but they also seem to be able to grow with great 
rapidity and they can live under all conditions—in deep water 
beyond the range of corals; in shallow water where they are 
*W. Saville Kent, The Great Barrier Reef of Australia, (1893), pp. 140-41. 
2 Agassiz, Bahamas, p. 104; Bull. Mus. Comp. Zodl., XXIV (1894). 
3 Agassiz, Three Cruises of the “‘ Blake,” I, 82. 
