34 THE VOYAGE OF H.M.S. CHALLENGER. 
DISTRIBUTIONAL AREAS. 
A sharp line of demarcation apparently separates the Reef-Coral fauna of the 
Atlantic on the one hand and the Pacific and Indian Oceans on the other (with the 
doubtful exception of sophyllia australis, which has been recorded from both regions 
by Milne-Edwards and Haime, Cor., 11. p. 375); though from the occurrence of Manicina 
«reolata in 20 fathoms water in Simon’s Bay, Cape of Good Hope, it may be doubted 
whether the two areas will prove to be so sharply defined. 
In the Atlantic, no definite districts can be made out, the fauna throughout beime 
essentially West Indian. 
In the Pacific and Indian Oceans, the fauna is characterised generally by more or less 
uniformity, exception being made, however, in the cases of the districts of the Sandwich 
Islands and the West Coast of America, each of which appears to be more or less markedly 
cireumscribed by the distinctness of the forms which flourish there. 
The Reef-Corals of Tahiti are similar in many respects to the Corals of the Red Sea, 
many species bemg common to both; while almost the same may be said of the Corals 
of the Friendly Islands, the Fiji Islands, and the Philippines. 
It must be confessed, however, that any attempt to generalise from the facts at hand, 
as to the relation of the fauna of the chief centres of coral growth in the Pacific and 
Indian Oceans, must be at least premature, and this owing to several causes. 
In the first place, for a large number of the species which have been described, more 
especially by the old authors, no definite locality is recorded; the locality being either 
altogether omitted or given under such vague terms as, ‘‘ Indian Ocean,” “ East Indies,” 
“ Austral Seas,” “ Australasia,” &c. 
In the second place, of the large collection of Corals in different museums but little 
is really known, owing to the want of published detailed reports or catalogues of the 
collections. 
And in the third place, while several voyages and expeditions have been accomplished 
through many parts of the coral regions during which collections have been made with 
more or less interesting results, yet no prolonged and exhaustive examination of the 
genera and species of Reef-Corals found in any one locality, excepting in the Red Sea, 
has yet been made by any practised naturalist ; so that our knowledge of the distribution 
of the Reef-Corals throughout the multitudinous islands and formations of the Indian 
and Pacific Oceans is, at the best, fragmentary and unreliable. 
It is a welcome sign, however, of the impetus which recent research has given to the 
study of the Anthozoa, that two practised naturalists are carrying on investigations into 
the fauna of certain districts of the Indian and Indo-Pacific Oceans and it cannot be 
doubted that extremely interesting additions will be made therefrom to our knowledge 
of the Corals of these regions. 
