394 
THE VOYAGE OF H.M.S. CHALLENGER. 
BATHYMETRICAL DISTRIBUTION. 
The Tetractinellida range from 0 to 1913 fathoms, the maximum depth being that 
recorded by Perceval Wright for Thenea muricata ( Wyville-thomsonia wallichii, 
E. P. W.), from the North Atlantic. The range of the species of the Challenger 
collection is from 8 to 1850 fathoms. 
In the following table the number of species in each of the groups of Sponges that 
have been described in the Challenger Reports is distributed in four columns, which are 
numbered I., II., III., IV., according as they were obtained from 0 to 50, 51 to 200, 201 
to 1000, 1001 fathoms and upwards. 
Table I. 
I. 
0-50 
Fathoms. 
II. 
61-200 
Fathoms. 
III. 
201-1000 
Fathoms. 
IV. 
Above 1000 
Fathoms. 
Tetractinellida, 
16 
23 
18 
8 
Hexactinellida, .... 
27 
43 
55 
Monaxonida, .... 
44 
45 
53 
25 
Ceratosa, .... 
13 
5 
3 
Calcarea, .... 
16 
16 
3 
In the next table, the number of species in the first column^ being taken as a basis, the 
numbers in the succeeding columns indicate the numbers of species which should have 
been found supposing they were equally distributed independently of the depth : — 
Table II. 
I. 
0-50 
, Fathoms. 
II. 
51-200 
Fathoms. 
HI. 
201-1000 
Fathoms. 
IV. 
Above 1000 
Fathoms. 
Tetractinellida, .... 
16 
20-5 
30 
72 
Hexactinellida, .... 
27 
39-51 
94-63 
Monaxonida, .... 
44 
56-375 
82-5 
198 
Ceratosa, .... 
13 
16-6 
24-37 
... 
Calcarea, .... 
16 
20-5 
30 
* In the case of the Hexactinellida, since there are no species in the first column, the number in the second has been 
taken as a base ; it would have been better (for purposes of comparison) if this had been done in all cases. 
