NO. 2 



OLGA hartman: submarine canyons 



69 



TANNER CANYON 



Number of all species and polychaete species 127/75; of all specimens 

 and polychaete specimens 1553/456. 



It can be seen that the highest number of species 'and specimens 

 (cumulative) has not come from Redondo canyon, from which the 

 largest number of samples originate, but from those samples which 

 have come from shallow, or shelf depths, where sediments are mainly 

 silty mud or sand, and where diversity is greatest. 



ON THE REPLACEMENT OF SPECIES IN THE 

 SUBMARINE CANYONS 



a. Replacement of species in successive canyons: — The replacement 

 of species in successive canyons, from northernmost to southernmost, 

 and from longshore to ofifshore locations, is best illustrated by naming 

 the species by canyons, in sequence from north to south and from 

 east to west. Because the polychaetes and echinoderms are most com- 

 pletely identified and consistently present, they are used to illustrate 

 the principles involved. Four hundred and one polychaetes and sixty- 

 one echinoderms are named. The occurrence of a species is indicated 

 by an X, and its absence (or unnoted presence) by a blank space. 



Listing the specific categories in this order, 37 species of polychaetes 

 are named from Monterey canyon. Twenty-three of these are common 

 to Hueneme canyon, and 69 others are added, including those named, 

 from no, 38, Aglaophamus sp., through no. 106, Travisia pupa (see 

 below). The sequence continues with Mugu, Dume, Santa Monica, 



