440 



THE VOYAGE OF H.M.S. CHAT.T.F.NGER. 



Of the ninety different species of Hexactinellids obtained on the Challenger 

 Expedition — 



24 species were found in the Atlantic. 



16 „ ,, Indian Ocean. 



57 „ „ Pacific 



But it is obvious that these figures taken by themselves, without reference to the 

 number of dredgings and trawlings, do not give any correct representation of the 

 abundance of Hexactinellida in the different regions. It is necessary to take into 

 account for each ocean the total number of dredgings or trawlings, and the proportion of 

 these which yield Hexactinellida. The percentage figures for the separate regions must 

 then be compared with the statistics of the whole expedition- 

 Out of the total 276 dredgings or trawling only 58 yielded Hexactinellida, which 

 gives a percentage of 21 '1 over the whole. Of the 125 dredgings or trawUngs in the 

 Atlantic 19 yielded Hexactinellida, i.e., a percentage of 15"2; of the 32 searches in the 

 Indian Ocean 11 were successful, i.e., 34'4 per cent.; of the 119 in the Pacific 28, i.e., 

 23 '5 per cent., were rewarded with HexactineUid booty. 



Thus we see that of the three oceans the Atlantic appears to be by far the poorest in 

 Hexactinellids, and in its percentage of 15 '2 is not a little below the general average 

 of 21 '1 ; while in contrast to this the Indian Ocean is richest, and in its percentage 

 of 34*4 is considerable above the average, which the Pacific with its 23 "5 per cent, only 

 slightly exceeds. 



If in the case of the two largest oceans the northern be estimated apart from the 

 southern haK, then the proportionate statistics stands as follows : — • 



From this it is apparent that the northern portion of the Atlantic is not so rich in 

 Hexactinellids as the southern, and that in the Pacific also the northern half is somewhat 

 surpassed by the southern. 



