NO. 2 



OLGA HARTMAN: SUBMARINE CANYONS 



97 



Offshore Canyons 



the outer edge of the shelf (Barnard and Ziesenhenne, 1961, p. 133). 

 In Redondo canyon its maximum numbers are much fewer, to 152 

 in 146 meters. In Coronado canyon it numbers 85 specimens in 123 

 m and 107 in 177 m. In Catalina canyon its numbers rise to 606 

 in 88 m (thus again like a shelf population), and reduce to 27 in 362 

 m. Other ophiuroid distributions are indicated in the analytical results. 



Another aspect of replacement or zonation, is that on the specific 

 level, where closely related species change with depth. This has been 

 illustrated for some of the polychaete families, Onuphidae, Lumbrine- 

 ridae, Orbiniidae, Glyceridae, and Capitellidae (Hartman, 1959, pp. 

 313-315). The same principle applies to other families and groups of 

 organisms. 



ON THE TOTAL NUMBERS OF SPECIES IN THE 



CANYONS 



The total numbers of species in most canyons are high, ranging from 

 262 in Newport canyon to only 43 in San Clemente rift valley. A break- 

 down of these values, from north to south, and east to west, and by 

 major systematic groups follows (the number of samples taken is given 

 in the last column) : 



Mt = Monterey, H = Hueneme, Mu = Mugu, D = Dume, Mo = 

 Santa Monica, Rsw = Redondo south wall, Rnw = north wall, Ra = axis, 

 Rsi=slope, Rf = fan, S = San Pedro sea valley, N = Newport, Sd = San 

 Diego trench, J = La Jolla, Co = Coronado, Z = Santa Cruz, Ca = Cata- 

 lina, CI = San Clemente rift valley, and T = Tanner canyon: 



