72 SIDNEY POWERS 
broad ridges separating a broad groove, the latter being filled with 
drifted shells which washed in after the surface was marked. 
Common strand markings have not been noted on the same 
slab with the most clearly defined grooves and ridges, but well- 
developed asymmetrical ripple marks, rill markings of various 
kinds, small irregular markings such as might represent worm 
Fic. 5.—Casts of irregular markings, depressions in the strand, which appear 
to represent fronds of algae which lay on the beach. Near the right lower corner 
there is a piece of sandstone in the groove which in the original specimen looks sus- 
piciously like the reverse side of a flattened stem of frond. Locality as in Figure 4. 
tracks or burrows or algae have been found on sandstones either 
of the same bed or of beds higher or lower in the series. There 
are also smooth lumps which might have been lumps of sandy 
mud, faint single grooves or ridges, and faint symmetrical ripple 
marks with or without minute, superimposed, tubular lumps and 
worm tracks, the whole glazed with a thin film of iron oxide as 
are most of the markings. 
