of Edinburgh , Session 1885 — 86 . 
861 
extremity of a branch. In addition there were mat-like growths 
of other Alcyonarians, resembling, but on a much more extensive 
scale, our common British Alcyonium. 
It will have been observed in the foregoing description that 
thickets of Porites Icevis principally usurped the depths between 
2 and 8 fathoms. Such, however, was not my usual experience in 
these localities, these depths on the lee sides of islands being 
generally occupied by arborescent and other branching Madreporce. 
In Selwyn Bay, on the lee side of Ugi Islands, these Madreporce 
throve in the shallower portion of the reef-coral zone in depths less 
than 10 fathoms; whilst Seriatoporce* seemed to prefer the deeper 
parts of the zone in depths of 20 fathoms. This accords with Mr 
Darwin’s experience on the leeward side of Mauritius.! It is 
manifest, however, that we have little or no acquaintance with the 
causes that favour or prevent the growth of particular species of 
corals in any one locality ; and thus we often meet with unexpected 
facts. For instance, the stout coral, Isopora labrosa (D.) is able to 
adapt itself to any situation, whether on the weather slopes of reefs 
in depths beyond 5 fathoms, or on the dark muddy bottom of man- 
grove-skirted channels, or in the clearer water of lagoons. I might 
mention several other examples of the same kind amongst certain 
species of Porites and Millepora. A species of Madrepora, f that 
commonly came up in my soundings from depths of 8 to 12 
fathoms on the weather slopes of reefs, appeared in one locality to 
flourish at similar depths on the lee or protected side of an island. § 
I come now to refer to the corals that grow in the interior of 
lagoons and lagoon-channels. A large extent is occupied by sand 
and chalky mud ; but in the shallower portions, and especially in 
those situations which are near the breaks in the reef, corals thrive 
in great profusion. These quiet waters are more particularly the 
home of the foliaceous and branching corals. Amongst the former 
may be observed Turbinaria frondens (D.), Merulina ampliata (E. 
& S.), Oxypora contorta (Quelch), and species of Pachyseris , 
* Probably a new species, as Mr Ridley informs me. 
t Coral Reefs, 1842, p. 81. 
X This coral, according to Mr Quelch, closely resembles M. cerealis of the 
West Indies. Its range of depth appears to be 2 to 13 fathoms. 
§ For some further particulars of my coral-soundings, vide a short paper iii 
the Annals and Magazine of Natural History, June 1884. 
