460 



THE VOYAGE OF H.M.S. CHALLENGER. 



This table reveals at once the remarkable fact that a large number of localities 

 yielding Hexactinellids, and a rich abundance of species occurred in moderate depths of 

 95 to 200 fathoms, while the depths from 200 to 300 are quite without Hexactinellids, 

 which become again more abundant both in localities and species at dejDths from 301 to 

 700 fathoms, disappearing again in depths between 701 and 1000, and finally occurrino- 

 in moderate abundance between 1000 and 3000 fathoms. 



If regard be first had only to the number of Hexactinellid localities and their per- 

 centage among the total number of dredgings and trawlings undertaken at the relative 

 depths, the following table represents the bathjanetrical statistics for successively large 

 ranges of 500 fathoms : — 



In the above summary one fact might possibly cause misunderstanding, namely, that 

 the first region is noted as 1 to 500, although it is well known that in the upper 94 

 fathoms no Hexactinellids whatever occur. If one excludes the dredgings or trawlings 

 not deeper than 94 fathoms, and regards the first bathymetrical region as 95 to 500 

 fathoms, then out of the total 63 dredgings or trawlings, 19 yielded Hexactinellids, 

 i.e., 30"2 per cent., which is a decidedly larger figure than that given in the table, 

 18 per cent. It is thus seen that most Hexactinellid localities were between the depths 

 of 95 and 1000 fathoms, while beyond this the frequency gradually decreases, finaUj- 

 disappearing below 3000 fathoms. 



K the number of species be considered in relation to the number of dredgings or 

 trawlings at the various depths, it is convenient to follow the plan of the large Table 

 VIII. (p. 456) and separate the region from 1 to 94 fathoms from that from 95 to 100, 

 and then to continue up to 1000 fathoms with ranges of 100, and with ranges of 500 

 up to 3000 fathoms. 



