ARTHROPHYCUS AND D^DALUS. 



205 



portion exhibits such features as bars, cross-lamination, oblique layer- 

 ing, current-crests, current-channels, erosional, ripple-marked, and 



Fig. 2. — Diagram showing gradation from Ihe vertical form of Da-dn/iis to the spiral. 

 c, cylinder; t, thin edge. 



sun-cracked surfaces, and occasionally surfaces covered with brecciated 

 matter or rolled balls of clay, indicating shallow water of fluctuating 



