PALEOBIOGEOGRAPHY OF THE MARINE REALM 189 



sediment-water interface of the flysch seas commonly produced a 

 regular pattern of searching and feeding tracks in the manner of 

 many organisms that work in darkness, and some of the deep-sea 

 photographs shown by the Soviet delegates to this Congress 

 showed remarkably flyschlike organic markings. 



I have previously approached this conclusion with more reser- 

 \ation (Cloud, 1959b, p. 944) simply because there has been so 

 widespread a trend, uncritically following Ph. H. Kuenen's 

 inspired lead and on what I consider less satisfactory evidence, to 

 interpret all flyschlike sediments as deep-water deposits and too 

 wide a range of sediments as flysch. However, the evidence so 

 briefly reviewed above does strongly suggest that the known 

 benthonic megafauna of the flysch facies as here defined represents 

 an infauna of relatively deep water: probably mainly bathyal 

 (below 200 m) and perhaps locally even abyssal. Evaluation of the 

 microfaunal assemblages of the younger flysch facies deposits 

 earlier led Ksiazkiewicz (1958, p. 419) and before him Grzybowski 

 (Ksiazkiewicz, 1956, p. 387) to a similar induction. As defined by 

 the markings left by its benthonic megafauna, moreover, the flysch 

 facies can be considered to represent the farthest ranged and 

 longest lasting paleobiogeographic realm (if it may be so called) 

 in the recorded history of the earth. This, to be sure, opposes both 

 the dictum that little is represented in the fossil record beyond 

 shelf elements, and the suggestion sometimes made that the 

 existing deep-sea fauna has evolved in younger geologic times from 

 invasion of basins that were stagnant through a preceding epoch 

 of little climatic dift'erentiation. The idea of general deep-sea 

 stagnation in the nonglacial geologic past is opposed not only by 

 the probable persistence of a long-ranged flysch facies fauna but 

 also by the antiquity of deep-sea elements such as the Mono- 

 placophora, by hadal endemism in general (Wolff, 1960, pp. 100- 

 102, 104), by the importance of oxygen-bearing turbidity current 

 sedimentation and oxidized sediments in the deep sea basins, and 

 by the certainty that there always was some temperature gradient 

 between equator and poles and some frictional turnover of the 

 water masses related to the opposing wind systems which must 

 exist in order to maintain the circulatory balance of the atmos- 

 phere. 



