260 
RIPPLED MARKINGS. 
this stone was in a state of loose sand at the 
bottom of the sea. Laminated sandstones are 
also often disposed in minute undulations, re- 
sembling those formed by the ripple of agitated 
water upon sand.* 
The same causes, which have so commonly 
preserved these undulations, would equally pre- 
serve any impressions that might happen to 
have been made on beds of sand, by the feet 
of animals ; the only essential condition of such 
preservation being, that they should have be- 
come covered with a further deposit of earthy 
matter, before they were obliterated by any suc- 
ceeding agitations of the water. 
The nature of the impressions in Dumfries- 
* In 1831, Mr. G. P. Sevope, after visiting the quarries of 
Dumfries, found rippled markings, and abundant foot tracks of 
small animals on the Forest marble beds north of Bath. These 
were probably tracks of Crustacea. — See Phil. Mag. May, 1831, 
p. 376. 
We find on the surface of slabs both of the calcareous grit, 
and Stonesfield slate, near Oxford, and on sandstones of the 
Wealden formation, in Sussex and Dorsetshire, perfectly pre- 
served and petrified castings of marine worms, at the upper ex- 
tremity of holes bored by them in the sand, while it was yet soft 
at the bottom of the water; and within the sandstones, traces 
of tubular holes in which the worms resided. The preservation 
of these tubes and castings shews the very quiet eondition of the 
bottom, and the gentle action of the water, which brought the 
materials that covered them over, without disturbing them. 
Cases of this kind add to the probability of the preservation of 
footsteps of Tortoises on the Red sandstone, and also afford proof 
of the alternation of intervals of repose with periods of violence, 
during the destructive processes by which derivative strata were 
formed. 
