REPOET ON THE TETRACTINELLIDA. 
891 
bifurcation of tbe equatorial current has not always been situated exactly off Cape St. 
Koque, but sometimes to the north of it, so here we meet with a general resemblance to 
Caribbean fauna, and with certain remarkable forms which are common to both. The 
Magellanic, South African, and South Australian provinces owe their existence to the 
westerly cold currents of the j4ntarctic. The Indo-Pacific province owes its wide exten- 
sion to the general easterly currents of the Indo-Pacific Ocean, which reach westwards as 
far as Africa, and on the north to Japan, where they furnish the Kuro Siwa, which 
probably peoples the greater number of the North Pacific Oceanic Islands. The Indo- 
Antarctic fauna is possibly the remnant of one once associated with that of an Antarctic 
continent, uow preserved in isolation by its remoteness from all other areas. 
The complete record kept by the Challenger of both successful and unsuccessful 
dredgings enables us to form some estimate of the relative richness in forms of the different 
distributional areas. In the following table the relation is given between the number 
of successful and unsuccessful dredgings for each of the three great oceans traversed by 
the Challenger 
Total Number 
of Dredgings. 
Number of 
Successful Dredgings. 
Per cent, of 
Successful Dredgings. 
Atlantic, .... 
129 
14 
10-9 
Indo-Antarctic, 
28 
4 
14-3 
Pacific, ..... 
120 
21 
17-5 
In the next table the relative richness of the same areas in species is given, the same 
species being counted twice when it occurs in different dredgings, which is, however, 
very seldom : — 
Total Number 
of Dredgings. 
Number of Species. 
Per cent, of Species. 
Atlantic, .... 
129 
15 
11-63 
Indo-Antarctic, .... 
28 
7 
25 
Pacific, ..... 
120 
42 
36-6 
The relative richness of the three areas, as given in the last table, may be approxi- 
mately represented by the following proportion : — 
Atlantic : Indo-Antarctic : Pacific = 1 : 2 : 3. 
