314 _ Seientifie Intelligence. 
(7.) The direction and temperature of oceanic currents (p. 112): 
this cause accounting for the non-distribution of central-Pacific 
species of corals to the Panama coast, and the paucity of species 
there, with the absence of the large Astrea group and the Madre- 
ores. 
On this last point I say in explanation, on page 112: “ Owing to 
the cold oceanic currents of the eastern border of the Pacific—one 
of which, that up the South American coast, is so strong and 
of Panama, is narrowed to 20°, which is 36° less of width than it 
has in mid-ocean; and this suggests that these currents, by their 
temperature, as well as by their usual westward direction, have 
proved an obstacle to the transfer of mid-ocean species to the 
warm-water species—from the West Indies or Bermudas, east- 
ward, to western Africa, is impossible. The width of the coral 
. 
I did not think to include among the causes a too rapid ei 
whic 
account, narrower than it would have been had the land been 
stationary. But the cause does not appear to me to have very 
many examples. 
(IL) The third sentence of the Preface reads thus 
established, falsify my generalization that voleanos in a state of 
action are not found within the area of subsidence, whilst they 
” 
sc at 
a 
