1857.] SALTER LONGMYND FOSSILS. 205 



In connexion with the facts above mentioned, which go to show 

 the great prevalence of Annehdes having the same habits as those of 

 the Lob-worm (Arenicola) of our coasts, it is worth while to remark 

 on the extraordinary abundance of animals of this class in Palaeozoic 

 times. 



In the Cambrian rocks of Ireland they are in almost as great 

 plenty as in Britain, and are there associated, as I have seen in com- 

 pany with Dr. J. R. Kinahan, who discovered them, with the matted 

 layers of Oldhamia. 



In the Liugula-flags of North Wales, e.g. near Maentwrog and 

 Ffestiniog, they abound wherever sandy sediment has been thrown 

 down ; but I have only yet seen them in the form of Scolites or 

 Helminthites, and have not yet found the double burrows in this 

 formation. 



In the Stiper Stones, as above noted, the Arenicolites (Scolithus) 

 linearis of Hall is the common fossil, occurring as long vertical tubes 

 with trumpet-shaped openings in the quartz-rock. And in the Tre- 

 madoc slates, the Llandeilo flags, and indeed all the Silurian series, 

 worm-tracks and burrows are frequent in strata which were once 

 sabulous mud. In the Upper Silurian rocks of Dingle, County 

 Kerry, I found the Arenicolites in flaggy sandstone. 



More lately these double burrows have been found in company 

 with fragments of land-plants in the Devonian fish-beds of Caithness, 

 and in those beds, of somewhat doubtful age, which Prof. Nicol has 

 described as carboniferous, on the borders of Loch Assynt in Suther- 

 landshire*, while they have now been long known as most plentiful 

 in the sandstones of the coal-measures. 



It is in the Carboniferous system, indeed, that they appear to have 

 attained their maximum in size and number. Throughout all the 

 lower beds of that system, as exhibited in Pembrokeshire, North 

 Devon, or the South of Ireland, the burrows of marine worms are 

 conspicuous, chiefly in the form of cylindrical masses, upon the sur- 

 faces of the beds or permeating them in all directions. They are of 

 various sizes, from the thickness of a crow-quill up to 2 or 3 inches 

 in diameter ! and often of great length ; and they frequently consti- 

 tute of themselves massive beds, the sabulous matter left behind as 

 ejected from the worm penetrating the more argillaceous beds in a 

 way that produces an exceedingly tough mass — not easily acted upon 

 by the waves — in shore-sections. 



The large annelide-tubes or casts in the carboniferous strata of 

 Cumberland, and the tracks upon the coal-measure flags at Kilkee, 

 County Claret, are well known, and are of a size greatly larger than 

 would be produced by the majority of living species. There is much 

 yet to be done in the study of marine worms, with a view to ascertain 

 the kind of impressions they leave in both sandy and argillaceous 

 sea-beds. 



* Quart. Journ. Geol. Soc. No. 49. p. 32. The arrangement of these burrows 

 appears to have led Prof. Nicol into the belief that he had found fragments of 

 Stigmaria, and may have influenced him in determining the age of the beds. 



t Edinb. New Phil. Journ. new ser. vol. i. p. 278. 



