454 PROCEEDINGS OF THE ACADEMY OF [Aug., 



Reef (text figure, S). Illustrates the abrupt northward (to the left) descent 

 of the marginal deposits (b) into the channel (see text figure, C) and the 

 truncation of the southward dipping shale (a) below. 



Fig. 2. — Northern margin of the Southern Reef. In this figure the reef itself 

 cannot be distinguished, but its base is shown by the top of the truncated 

 shale below the reef. The discordance between the line of truncation 

 (x, y) and the southward dip of the shale above the reef is also illustrated. 



Fig. 3. — Reef-margin deposits about the northern border of the Northern 

 Reef (see text figure, N). These deposits lie beyond the area in which 

 fanning occurs and their alternating hard and soft layers are essentially 

 parallel. The hard layers are limy and the soft layers are friable shale. 



