THE OSTEACODA. 



293 



Between 300-200 



400-300 



500-400 



750-500 



1000-750 



CONCHCECIA RHYNCHENA, MuUer. 



fathoms 

 this species 

 occurred in 



1 out of 3 hauls 



3 



2 

 1 



3 

 3 

 4 

 5 



with 0-33 

 1-33 

 3-00 

 1-20 

 0-24 J 



average 



specimens per 



100 fathom 



haul. 



This forms a typical mesoplanktonic distribution, yielding a regular spindle. 



CoNCHffiCiA E.OTUNDATA, MilUer. 



The following table shows the distribution (1) in the epiplankton, (2) of specimens at 

 Stage II. or earlier in the mesoplankton, and (3) of specimens at Stage I. in the 

 mesoplankton : — 



At 



Between 





 25 

 50 



75 

 100 



150-50 

 200-100 

 250-150 

 300-200 

 400-300 

 500-400 

 750-500 

 1000-750 



400-300 



500-400 



750-500 



1000-750 



1250-1000 



1500-1250 



1 



fathoms 

 this species 

 occurred in 



fathoms 



young 



specimens 



occurred in 



fathoms 



Stage I. 



occurred in 



15 per cent, of 13 hauls, with 0"1 "^ 



33 



38 

 90 

 88 



1 

 4 

 2 



1 

 

 

 2 

 2 



2 

 2 



4 

 3 

 

 1 



out of 



>> 

 » 



12 

 13 

 10 



17 



1 

 7 

 3 

 3 

 3 

 3 

 4 

 5 



3 

 3 

 4 

 5 

 3 

 2 



1-9 



4-6 



62-2 



14-3 



6-0 

 4-8 

 0-6 

 0-6 

 0-0 

 00 

 0-3 

 0-1 



1-0 

 1-6 

 0-5 

 0-4 

 00 

 0-4 



average 



specimens 



per hour 



haul. 



average 

 specimens 



per 



100 fathom 



haul. 



The general distribution was that of curta. We have a species which had a plurimum 

 at about 75-100 fathoms, but extended to the surface. Down to about 200 fathoms the 

 smaller specimens, Stage II. or younger, were fairly plentiful. Their lower limit would 

 seem to be at about that level, and I regard at any rate most of the few small specimens 

 caught at greater depths as dead or dying, or perhaps sinking for their last moult. On 

 the other hand, the larger specimens at Stage I. seem to attain a plurimum between 

 500 and 300 fathoms. It is not suggested that no large specimen ever rises into the 

 epiplankton, but that the oldest stage as a whole seeks deeper water. 



47* 



