8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 92 



phosed and sheared, and since the fossils are not distorted, it is Hkely 

 that originally they occurred in a limestone pebble forming a part of 

 the conglomerate. This, therefore, raises the question as to whether 

 the conglomerate is of Cambrian age or younger. 



PRESENT CAMBRIAN DISTRIBUTION 



With the data furnished by these recent discoveries, the general 

 picture of Cambrian distribution has been considerably altered, and 

 several generalizations become possible. 



The Lower Cambrian is still unknown both throughout the Southern 

 Rockies and in the northern division as far north as the Bow Valley, 

 near Lake Louise, Alberta. This statement, of course, disregards the 

 possibility that the Cranbrook occurrence in the Rocky Mountain 

 Trench should be included with the Rocky Mountains and not placed 

 in the Selkirk system. On the other hand, the distribution of the 

 Lower Cambrian has been extended in the ranges west of the Rockies 

 a considerable distance farther south than it was formerly known 

 to occur. 



Middle Cambrian distriluition was expanded to a greater extent. 

 In the Rocky Mountain system it has reduced the Beltian gap to 

 several hundred miles, and to the west its range has been expanded 

 equally with that of tlie Lower Cambrian. 



On the other hand, the Upper Cambrian received no unquestioned 

 additions, so that the Deadwood series still constitutes the sole record 

 in the Southern Rockies and retains approximately its previously 

 known distribution to the north. 



DEDUCTIONS REGARDING CAMBRIAN SEAWAYS 



When Lower Cambrian seas first penetrated the continent in western 

 North America, it appears to have been along a single great geosyn- 

 cline, the complete course of which was outlined by Philip King (1933) . 

 Judging from Lower Cambrian occurrences, it seems that this geosyn- 

 cline developed by growing simultaneously from its two extremities. 

 Thus Lower Cambrian waters entered its southern portion, the Great 

 Basin geosyncline, and passed through what is now southern Cali- 

 fornia as far northward as central Nevada and Utah. From the north, 

 marine waters apparently came down from the Arctic to northeastern 

 Washington, leaving an unoccupied gap of several hundred miles, 

 because existing evidence does not indicate removal of Lower Cam- 

 brian here prior to deposition of the Middle Cambrian. It will be 

 noted that this interpretation considers the existence of but one geo- 



