FORMATIONS AND PHYSICAL HISTORY 347 



Fig. 310. Map showing the Upper Cambrian formations. The outcrops are 

 shown in black. The continuous lines represent areas where the Upper Cambrian 

 formations are confidently believed to exist, though concealed. The dashes repre- 

 sent areas where there is some reason for believing them to exist. The dotted arras 

 represent areas from which the Upper Cambrian is believed to have been removed 

 by erosion. The unshaded areas have the same meaning as in Fig. 309. 



