58 _ PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 24, 
water at Aden. A Manicina of the Caribbean is found on the coast 
of Brazil. Mr. Darwin has given me some deep-sea corals from 
Cape Verde, and one is identical with a species found in the shallow 
sea between Cuba and Jamaica. Plesiastrea has species at Panama 
and Port Jackson. Rocks are often incrusted with reef corals— 
at Zanzibar and Ceylon for instance. 
These exceptions are all within the range of the external condi- 
tions favourable for the existence of reefs, and the species retain the 
structural peculiarities which differentiate them from the deep-sea 
corals noticed at the commencement of this essay. 
VII. Excrprionat RELATIONS OF THE TWO FauNas. 
The genus /labellwm, which has species in the deep seas of west- 
ern Europe, has others in the deep seas between the coral archi- 
pelago and the Asiatic continent, and some which are found in the 
reefs of the Fidji and other islands. There is a Desmophyllum in 
the West-Indian coral area, and Caryophyllie also. Dendrophyllia 
has a species in the China seas within the range of the conditions 
favourable for reefs. 
There is no well-established stance of any species or variety 
known to belong to the true coral fauna of reefs, lagoons, and shal- 
lows, within the range of the coral seas, which can be identified with 
any member of the deep-sea coral fauna of the offing of continents 
and large islands remote from the coral tracts. 
As yet nothing is known about the corals of the depths between 
the coral islands of the Pacific Ocean, or of the inhabitants of the 
great sea-desert to the west of America; but Mr. Christy gave me a 
collection of corals he had dredged up between Cuba and Jamaica 
in not very deep water, and I found the species to be closely allied to 
and identical with those of the lagoons of the reefs*. 
From what is known at present, then, the existence of two coral 
faunas must be admitted—one restricted to large portions of the 
world, where the conditions favourable for reefs exist, and the other 
confined to the littoral tracts, and deep and abyssal seas near cer- 
tain continents. Both depend upon the persistence of definite ex- 
ternal conditions, and neither could flourish on each other’s area or 
in such seas as the Baltic or the Black Seat. 
It must be remembered, however, that coral reefs are not inva- 
riably found where the physical conditions which accompany them 
elsewhere exist. The few islands in the Atlantic are not surrounded 
by reefs, probably on account of the impossibility of the migration 
of Madeporarian ova to them. The Bermudas are exceptions; but 
their position in reference to the Gulf-stream explains their haying 
a coral fauna of the reef kind. 
When the details of the marine deposits of the Mesozoic and 
Cainozoic strata are studied, it becomes evident that some of them 
contain fossil corals belonging (so far as can be judged from the 
* Consult Pourtales, op. cit. 
+ The abyssal fauna exists off Florida, and enters the reef area. See Pourtales, 
op. Cit. 
