pH actually did go below 7. 



Oppenheimer: How soon after you collected the samples did you read it? 



Bradley: We did it in place. 



Stevenson: I might just comment on that. 1 found pH's similar to those that 



Dr. Oppenheimer must have found as low as 4. 9 although that 

 was extreme, but certainly well below 7 - in the 6 and 5 range. 



Burbanck: I just wanted to ask about Limulus. It seems to leave such a 



good trail, but it was not mentioned. It is an old group and 1 

 just wondered if this came into the picture at any time in your 

 fossil trails. 



Hantzschel: Yes. You know the famous paper of Kester published in the 



German Paleontology, I think in 1938, on investigations founded 

 on observations on the east coast of the United States. It is a 

 very good investigation of the Limulus trails. There are trails 

 in the upper Jurassic of Germany. There are Limulus trails 

 in, I think, the Devonian of Pennsylvania. In Germany in the 

 famous upper Jurassic slates which preserve such wonderful 

 fossils. 



Burkholder: I wanted to ask if anyone studied the trails and burrows made by 

 animals in deeper water where the sediment is not exposed, for 

 example, with underwater cameras. 



Hantzschel: Not yet. There are only some submarine photographs taken by 

 deep sea expeditions. In some cores taken by deep sea exped- 

 itions there are also to be found such burrows, and sedimentologists 

 ologists do not like them because they stir up the stratification 

 and sedimentation. 



Redfield: I would suspect that under water an animal would leave a very 



weak trail because most of them don't weigh very much. 



Burbanck: 1 think that Ewing's pictures of the holothuroidian left quite a 



good one. 



Chronic: This brings up the big subject of dinosaur tracks and other ver- 



tebrate organisms which have had a tremendous amount of writ- 

 ing in the literature. Have you made any studies of these or any 

 possible paleoecological implications of these which concern the 

 tracks of vertebrates ? 



Hantzschel: We omitted the tracks of vertebrates. In Germany some distinct 

 trails that were said to be made by dinosaurs we found were worm 

 trails. 



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