10 PROCEEDINGS OF THE NATION AL MUSEUM. vol.43. 



It is interesting to note in this connection that there are more 

 species common to Japan and the west coast of North America than 

 to the Hawaiian region and the west cohst of North America.^ 



An inspection of the table headed " Bathymetrical distribution" 

 shows that the depth between 100 and 200 fathoms yielded the best 

 results, 45 species being secured from that depth. The depth of from 

 50 to 100 fathoms appears to come next in order, with a record of 41 

 species, although a less range of depth is here included than in the 100 

 to 200 fathom column. A very common source of error in discussing 

 such tables lies in the fact that no attention is ordinarily given to the 

 number of hauls taken in each zone. 



An examination of the records shows that alcyonarians were 

 secured from 75 stations during the cruise. A depth of 1 to 50 

 fathoms is recorded for 8 stations, 50 to 100 fathoms at 22 stations, 

 100 to 200 fathoms at 14 stations, 200 to 500 fathoms at 18 stations, 

 500 to 1,000 fathoms at 12 stations, and over 1,000 fathoms at 4 sta- 

 tions. Calculating the number of species to 100 stations in each of 

 these zones, we reach the following result: 



In the 1 to 50 fathom zone the rate was 162 species to 100 hauls. 



In the 50 to 100 fathom zone the rate was 200 species to 100 hauls. 



In the 100 to 200 fathom zone the rate was 333 species to 100 hauls. 



In the 200 to 500 fathom zone the rate was 172 species to 100 hauls. 



In the 500 to 1,000 fathom zone the rate was 200 species to 100 hauls. 



In depths of 1,000 fathoms or more the rate was 225 species to 100 

 hauls. 



Tliis shows still more clearly that the richest grounds were at depths 

 between 100 and 200 fathoms. In order, however, to compare zones 

 of equal depths we should add the 1 to 50 fathom and the 50 to 100 

 fathom zones, in order to compare with the 100 to 200 fathom zone. 

 When this is done we find that the zone 1 to 100 fathom yielded species 

 at the rate of 183 to 100 hauls, which still further emphasizes the 

 difference between the two; showing that the second, or 100 to 200 

 fathom zone, yields twice the number of species to 100 hauls that were 

 secured at depths under 100 fathoms. 



Below 200 fathoms the ratio is still maintained fairly well, the 

 average being about two species to each successful haul at all depths 

 explored. The number of hauls, however, in the deeper zones was 

 too small to give conclusive evidence. It nevertheless indicates, in a 

 general way, that the bathymetric distribution is more equable than 

 has generally been supposed, and that the deeper zones seem to yield 

 as much in proportion to the number of successful hauls as the 

 shallower, with the exception of the 100 to 200 fathom zone, which 

 seems particularly adapted to alcyonarian life. 



1 A discussion on this point will be found in my Descriptions of Hawaiian Alcyonaria, Proc. U. S. Nat. 

 Mus., vol. 34, 1908, p. 548. 



