NO. 24 PTARMIGANIA STRATA RESSER 5 



In 1912 G. B. Richardson (1913) of the United States Geological 

 Survey, assisted by P. V. Roundy, began the mapping of the Randolph 

 quadrangle, which lies east of Blacksmith Fork. He discovered an 

 isolated Cambrian outcrop in Laketown Canyon, where only a portion 

 of the sequence is exposed. He also found that the Middle Cambrian 

 is exposed on the eastern slopes of the Bear River Range throughout 

 the quadrangle with particularly good sections just north of Garden 

 City, in the upper St. Charles Canyon, and on Mill Creek. The full 

 report of the work in the Randolph quadrangle is now in press. 



Between 1923 and 1930 I saw all the mentioned sections except 

 Mill Creek west of Liberty. This locality was not located during 

 those seasons because nearly every geographic name in the vicinity 

 had been changed when the topographic sheet was published in 191 1. 

 Recently it has been possible to interpret these changes from old 

 notes and labels, and the Spence shale locality has been relocated by 

 Bishop Paul A. Spence, of Garden City, the son of the original 

 discoverer. In the following discussion use is made of the original 

 notes of Walcott, Blackwelder, and myself rather than of Walcott's 

 published composite section. Much of the information derived from 

 the mapping of the Randolph also is available. 



Paleontologic material.- — As listed below, fossils are described 

 from all the mentioned sections. All of Richardson's collections are 

 also in hand. While descriptions are confined to the Ptarmigania 

 fauna and species supposedly belonging to it, the other fossils from 

 the base of the Middle Cambrian to the top of the Ute formation were 

 examined in order that the position of the Ptarmigania fauna could be 

 understood. The fossils from the overlying strata are to be published 

 shortly, many species having now been described in manuscript. 



Further details respecting number of species, quantity of speci- 

 mens, and the matrix in which they are preserved will be found 

 subsequently in the description of the sections. 



CAMBRIAN DEVELOPMENT 



The general distribution of the Cambrian in the northern Wasatch 

 region has been described. A few facts regarding its development 

 are now in order. In the following paragraphs the absence of Lower 

 Cambrian beds and the formational subdivisions of the Middle Cam- 

 brian are briefly discussed. Descriptions of the formations are not 

 repeated because the definitions given by Walcott and Deiss suffice. 

 However, considerable detail will be found in the discussion of the 

 sections, where unpublished notes are also presented. 



