282 Professor Harkness on 



often, as already stated, see these more perfect tracks becom- 

 ing less distinct, leading to the inference, that while some 

 portions of the bottom of the sea, occupied by this lighter mud 

 were comparatively hard, others were so soft as to flow in 

 and in part efface the impressions. This is a circumstance 

 which occurs not only with annelid tracks, but likewise with 

 the impressions of reptilian footprints, as these are seen on 

 some of the faces of the Bunter sandstone strata. In this 

 latter case, although the conditions under which footprints 

 were formed were different, being generally the result of the 

 wanderings of reptiles on a sandy shore ; still the cause of their 

 partial obliteration was the same, namely, the flowing of sand 

 saturated with water into the impressions after the foot had 

 been removed. 



The occurrence of annelid tracks is not confined to the flag- 

 stones of the county of Clare, although these possess characters 

 which are the most perfect and beautiful of any which have 

 hitherto been discovered. They are met with in many of the 

 palaeozoic rocks, and frequently under the same conditions in 

 which they occur in this locality, namely, on the surfaces of 

 the flagstones. Sir Roderick Murchison, in the Silurian sys- 

 tem, figures a track from the schistose building stone of Llam- 

 peter, which he calls Nerites Sedgwicki, and this has a great 

 resemblance to the impressions on the flags of the county of 

 Clare. Markings of a similar nature also occur among the 

 lower Silurians of the south of Scotland, and have been named 

 Crossopodia by Professor M'Coy, and described by him in the 

 account of the fossils added by Professor Sedgwick to the 

 Woodwardian Museum. Tracks somewhat resembling those 

 of the county of Clare, both in nature and age, are mentioned 

 also by Mr Binney, as being present in the flagstones of Hut- 

 ton roof, near Lancaster ; and these are described by him in 

 the Transactions of the Literary and Philosophical Society of 

 Manchester, vol. x., p. 189. This geologist also mentions an- 

 nelid markings which are found in the form of holes in the 

 flags of the lower portion of the Lancashire coal-field ; and the 

 upper portion of these holes seem to have a great affinity to 

 the funnel-shaped cavities which the entrances into the bur- 

 rows of the annelids present, as they are seen on the surfaces 



