Each print was carefully examined by means 

 of an illuminated table magnifier and the re- 

 sults of this examination recorded on a stan- 

 dardized form. In addition to statistics con- 

 cerned with the operation of the camera, the 

 station number and location, this form details 

 the sedimentary and organic features observed 

 within the photographs. 1 These include the in- 

 ferred texture of the bottom sediment ; the na- 

 ture, orientation and dimension of ripple- 

 marks and other features indicating current 

 movement, including oriented organic struc- 

 tures; the occurrence and relative abundance 

 of shell, and the presence of living organisms 

 and their traces. 



1 Copies of the completed forms used in this study 

 have been lodged with the National Oceanographic 

 Data Center, Washington, D.C. The original negatives 

 and prints are housed in the collection, Division of 

 Sedimentology, U.S. National Museum, Washington, 

 D.C. 20560. 



The dimensions of objects and structures in 

 the photographs can generally be determined 

 by comparison with the compass shadow as de- 

 scribed earlier or by relation to other objects 

 of known approximate diameter in the photo- 

 graph, such as sand-dollars, etc. The texture of 

 the sediment forming the bottom may be indi- 

 cated directly (as in the case of gravel or 

 coarse sand) or it may be inferred from asso- 

 ciated features, such as ripple marks. For ex- 

 ample, the firmness of the bottom and the pro- 

 portion of mud (clay and silt) in the sediment 

 is indicated by the character of the mark made 

 on the bottom or the nature of the cloud of sed- 

 iment raised by the compass or vane striking 

 the sea-bed. The size and character of sedimen- 

 tary structures and of organic tracks, burrows 

 and mounds provide further evidence of the 

 nature of bottom sediment type. 



11 



