3y (0 PI. XV : n = Briokeai-th ; S=Arctio Bed, cut off by an oblique stream of sand, c ; fZ=Edge of a large 

 mass of iron-ceiuenfced gravel; c=A Fallen block of tbe same. /■=Liiie of fallen juaterial at the base 



Quart. Joum. Geol. Soc. Yol. LXYIII, PI. XY. 



