R. W. H. ROW—REPORT ON THE SPONGES : NON-CALCAREA. 383 
Ceylon fauna is extremely closely allied to the Australian, and though 
the list of species common to both Ceylon and the Red Sea has been 
increased since 1904 (when Professor Dendy’s work was written) from 
14 to 25, yet the gap is still clearly apparent when examining two collections 
from the different areas at the same time. 
Of the relation of the Red Sea fauna to that of Hast Africa it is more 
difficult to speak. Very little indeed has been done since Ridley’s report 
on the ‘Alert’ sponges (23), many of which came from this region. 
vertainly the number of species known has been increased since then, but 
even now the number does not approach that known from either the Red 
Sea or Ceylon. Keller, however, in 1891 (18) decided that the faunas of 
the Red Sea and Hast Africa were closely allied ; and Mr. Crossland, when 
writing an introduction to the series of reports of which this forms one, 
came to the same conclusion, though in the latter case the material on which 
the conclusion was based was not spongological but general. 
The above opinion of the area and subdivisions of the Indo-Australian area 
has been expressed in Table B, and there both the eastern and western 
divisions have again been subdivided, in order to show as clearly as possible 
the distribution of the various species over the area. For the purposes of 
the subdivision Ceylon has been considered separate from the Australian 
region, and the Red Sea has been shown separately from the Hast African 
region. It must be noticed that the Australian region, as defined in this 
paper, exactly corresponds with the Indo-Australian area as defined by the 
‘Challenger ’ report. 
Another group of sponges which occurs in the Red Sea also deserves 
attention. There are three species, long only known from the Mediterranean 
(in which they are common), which are now found also in the Red Sea. 
They are Leucandra aspera, Placortis simplex, and Euspongia zimocca. It 
is difficult to say anything definite as to the occurrence of these sponges in 
the Red Sea, but I think there is very great probability that they have come 
there by migration through the Suez Canal. 
That such migration can, and actually does, take place, Keller (18 a) gives 
ample proof, and I think the fact that all three of these species have been 
obtained at Suez is a strong support of the theory that they have migrated 
from the Mediterranean to the Red Sea. 
LINN. JOURN.—ZOOLOGY, VOL. XXXI. 30 
