1856.] 



SALTER LONGMYND FOSSILS. 



251 



tened (a), folded (6), and very often obliterated. All these various 

 conditions are represented in one figure (woodcut, fig. 2), which 

 thus gives an average idea of the appearance of the markings when 

 perfect. The furrows themselves either slightly impress a plain sur- 

 face, as at a ; or run between convex ridges, as at c, when they are 

 closer and more branched. 



Fig. 2. — Diagram of the restored form of peculiar Ripple-marks on 

 the Surfaces of the Flagstones near Church Stretton. 



All these circumstances and the great irregularity of outline con- 

 vinced me, after careful search, that these were not fucoidal impres- 

 sions *, but mechanical markings produced by the minute drainage of 

 the surfaces when the water retired ; and hence that they afford 

 proofs of quiet littoral action. 



Had the surface been merely sand, however fine, it is probable 

 that no such marks would have been produced, but that simple per- 

 colation would have taken place. But if a thin film of ochreous mud, 

 now a mere stain, were deposited on the surface, or washed into the 

 ripple-hollows, such a surface, being more retentive, might show the 

 tracks of the minute runnels of water as they flowed towards the 

 lowest part of the hollow before they were absorbed . 



This seems but a slender datum on which to found a belief of the 

 proximity of land in these old Cambrian deposits. Their arenaceous 

 character, however, and the conglomerates which occur a little higher 

 up in the series, are better indications. 



The conglomerates themselves, 120 feet thick to the W. of the 

 Portway, are well deserving study. They are chiefly round pebbles 

 of quartz-rock and vein-quartz ; but there is an occasional stray pebble 

 of syenite among them, as well as a great deal of felspathic matter de- 

 rived no doubt from the degradation of still older volcanic shores. 



* Such as those described under the name of Dadalus by Marie Rouault, Bull. 

 See. Geol. France, 2de Ser., 1850, vol. vii. p. 736. 



