1918] Essenhcrg: Distrihuiion of the Polynoidae 179 



II. Bathymetrical Distribution 



An attempt is here made to group the Polynoidae according to 

 their bathymetrical distribution. The different bathymetric groups 

 although less strictly defined than those of horizontal distribution 

 (tables 1, 2) are nevertheless recognizable. One difficulty with this 

 system of bathmetric grouping is that of trying to fit Polynoidae of 

 the entire coast into groups according to their bathymetric distribu- 

 tion disregarding their horizontal distribution. Consequently the 

 results are expected to be less definite on account of the diverse environ- 

 mental conditions at the different latitudes and at the different deptlis. 

 As is shown in table 3, there are very few species that are strictly 

 limited to one bathymetric zone, but they usually occur in one or more 

 adjacent zones. On the whole it is found that certain species desig- 

 nated as littoral may occur in the next greater depth, but as a rule they 

 are not found in very great depths, while on the other hand species are 

 found in deep waters which are never found in littoral zones above 

 one hundred fathoms. Consequently there is sufficient reason for sub- 

 dividing the species on the basis of their bathymetric distribution into 

 littoral, sublittoral and deep water species. 



Table 3* 

 Bathymetrical Distribution of the Polynoidae 



Depth in fathoms 



30-100 100-500 500-1000 1000-5000 Exceptional cases 



-^ .- 291-298 fathoms 



off San Nicholas 

 Island 



One specimen found 

 in 90 fathoms deep 



' In table a tne bathymetrical distribution of the Polvnoidae is shown. The depths are 

 sriven in five columns, 0-30. 30-100, 100-500, 500-1.000. 1,000-5.000 fathoms, x signifies 

 the presence of the species in that depth. Species found about and beyond the depth of 100 

 fathoms are considered in this article as deep water species. Absolute littoral species are 

 considered those inhabiting the shallow shore waters to the depth of 30 fathoms. 



