284 



DE. G. H. FOWLEE— BISCATAN PLANKTON ; 



CONCHffiCIA BRACHYASKOS, MuUer. 



This appears to have been another deep-water form ; it occurred only : 

 Between 300-200 fathoms in 1 of 3 hauls, with 0-33"' 



0-33 

 MO ^ 

 0-24 

 0-4oJ 



average 

 specimens per 

 100 fathom 

 haul. 



CoNCH(ECiA CURTA, Lubbock. 



The following table, in three parts, gives the distribution (1) in the epiplankton in the 

 usual manner; (2) of " small" specimens, at 0*8 mm. or less, in the mesoplankton ; and 

 (3) of large specimens, at Stage I. of 0'9 mm. or more, in the mesoplankton : — 



At 



25 

 50 



75 

 100 



Between 150-50 

 200-100 

 250-150 

 300-200 

 400-300 

 500-400 

 750-500 

 1000-750 

 1250-1000 



Between 500-400 



750-500 



1000-750 f 



1250-1000 j 



fathoms 

 this species -^ 

 occurred in 



^ 38 per cent, of 13 hauls, witli 4"1 "] 



58 



69 

 , 80 

 I 82 



r 1 out of 



12 

 13 

 10 

 17 



1 



fathoms young 

 specimens 

 occurred in 



1 fathoms f 



Stage I. 

 occurred in 



3 

 4 



I . 



34-9 



11-3 



(;i-3 



7-9 



70 

 3-8 

 2-6 

 0-6 

 0-3 

 1-3 

 1-8 

 0-1 

 01 



0-6 

 1-5 

 0-4 

 01 



average 



specimens 



per hour 



haul. 



average 



specimens per 



100 fathom 



haul. 



From this table may be inferred : — (1) That the numerical centre of distribiition of the 

 smaller specimens was in the lower part of the epiplankton. Taking the percentage of 

 hauls in which the species occurred as well as the average specimens per hour haul *, 

 one may say that the centre was between 25 and 75 fathoms, probably nearer to 75 than 

 25. This conclusion is for the whole twenty-four hours, neglecting day and night. The 

 night hauls are analysed below (pp. 285, 303). (2) That the large specimens (0-9 mm. or 

 more), which were only taken below 400 fathoms, were probably at home at those 

 depths, like the larger specimens of rotundata. (3) That it is to be noted that there was 

 a very sharp drop in the numbers of small specimens per 100 fathom haul somewhere 



* The high values for the total catches at 25 and 75 fathoms, when that at 50 fathoms was eompuratively small, 

 have been noted in some other cases. Here the high figure at 25 fathoms is due to two late evening hauls, of 12G 

 and 155 specimens ; the remaining ten hauls only produced in all 138 specimens. Compare pp. 302, 303, 



