PROCEEDINGS OF THE UNITED STATES NATIONAL MUSEUM 



isued 



SMITHSONIAN INSTITUTION 



U. S. NATIONAL MUSEUM 

 Vol.89 Washington: 1941 No. 3104 



A SUPPOSED JELLYFISH FROM THE PRE-CAMBRIAN 

 OF THE GRAND CANYON 



By E. S. Bassler 



The search for fossils in pre-Cainbrian rocks has always intrigued 

 the geologist, but the comparatively few discoveries have led to 

 almost as many controversial discussions, some of which are now 

 classic in the literature. Pre-Cambrian fossils so interested the late 

 Dr. Charles I). Walcott that he spent many months of his long, busy 

 life in the discovery and interpretation of their remains. Shortly 

 after his death. ]Mrs. Mary Vaux Walcott. in memory of her husband, 

 established the Charles Doolittle Walcott medal and honorarium, to 

 encourage further researches upon the paleontology of the earliest 

 sedimentary rocks. The outcrops of the little metamorphosed pre- 

 Cambrian strata in which fossils might be expected are usually in 

 more or less inaccessible regions where collecting presents difficulties 

 other than those of finding s})ecimens. Besides, the few fossils found 

 have led to the belief that these strata instead of being marine might 

 have originated u}>on the ancient continents. 



The paucity of marine fossils in pre-Cambrian rocks makes it im- 

 possible to solve the problem of their origin. However, there must 

 have been valid reasons for their apparent absence, since life wase 

 necessary at this time to account for the great abundance in the 

 succeeding Cambrian rocks. Prof. William Keith Brooks believed 

 that these oldest organisms lived at the surface of the ocean and 

 lacked hard parts because the weight of the skeleton would have 

 been detrimental to them. Dr. Walcott thought the pre-Cambrian 

 strata were fresh-water deposits in lakes of low calcium content 

 located considerable distances inland. Prof. T. C. Chamberlin sug- 

 o-ested that all organisms originated on the land and did not reacli 

 the sea until early Paleozoic times. Daly's theory was that the ])re- 



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