2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



1891a, pp. 594-595] I said, when speaking of the " Origin of 

 Fauna " : 



If we attempt to classify the Olenellus fauna by its genesis, an almost 

 impenetrable wall confronts us. That the life in the pre-Olenellus seas was 

 large and varied there can be little, if any, doubt. The few traces known 

 of it prove little of its character, but they prove that Hfe existed in a period 

 far preceding Lower Cambrian time, and they foster the hope that it is only 

 a question of search and favorable conditions to discover it. As far as known 

 to me, the most promising area in which to search for the pre-OIenellus fauna 

 is on the western side of the Rocky Mountains in the United States and on 

 their eastern (western) slopes in British Columbia. There the great thick- 

 ness of conformable pre-Olenellus zone strata presents a most tempting field 

 for the student collector. Another of the known possible areas is that of 

 New York and Vermont, but the prospect is not as favorable as in the West. 

 Other and better fields may exist in Asia and Africa, but as yet they are 

 unknown, with the exception of the areas described by Baron Richthofen in 

 China [Richthofen, 1882, Vol. 2, pp. 94, 100, and loi] where a great thickness 

 of conformable sedimentary beds exists beneath a horizon that is comparable 

 with the Middle Cambrian of western North America. 



With the above thought in mind I have for the past eighteen 

 years watched for geological and paleontological evidence that might 

 aid in solving the problem of pre-Cambrian life. The great series 

 of Cambrian and pre-Cambrian strata in eastern North America from 

 Alabama to Labrador ; in western North America from Nevada and 

 California far into Alberta and British Columbia, and also in China,^ 

 have been studied and searched for evidences of life until the con- 

 clusion has gradually been forced upon me that on the North Ameri- 

 can Continent we have no known pre-Cambrian marine deposits con- 

 taining traces of organic remains, and that the abrupt appearance of 

 the Cambrian fauna results from geological and not from biotic con- 

 ditions. I do not mean by this to infer that Brooks' hypothesis 

 [Brooks, 1894, pp. 455-479] of the origin of the earlier forms of 

 life in the surface waters of the open ocean is incorrect, but I mean 

 that we have no known record in the strata of the marine life of 

 the period between those earlier open-sea forms and the first records 

 of life found in the Lower Cambrian strata. That such life existed 

 there can be no question. It is the imperfection of the geological 

 record as known to us that is the cause of the present uncertainty 

 as to the pre-Cambrian faunas, and the abrupt appearance of the 

 Cambrian fauna. 



It is my present view that the known later Algonkian rocks in- 



^ Willis and Blackwelder, 1907, Vol. i, pt. i, pp. 21-44, 99-156, 265-274. 



