R. Etheridge, jun.— Carboniferous Tubicolar Annelida. 217 
this a character one would more readily expect to find associated 
with an ally of Sprrorbis, to which it would matter little whether its 
object of attachment had or had not sustained damage from con- 
tinuous aqueous action ? 
Unfortunately for the argument of Van Beneden and Coemans, 
Microconchus or Palgorbis is as frequently found adhering to the 
surface of shells as to the fronds of ferns, and portions of other 
plants. Mr. E. W. Binney ! long ago described the manner in which 
the Unios (Anthracosiz) found on the roof of the Four-feet Mine at 
Bradford were covered with this little organism; and I have myself 
incidentally pointed out its like association with one of the bivalves 
of the Wardie Shales, Anthracomya Scotica (mihi). This and another 
allied form, Anthracoptera obesa (mihi), are sometimes so covered 
with individuals of Iicroconchus, that it is difficult to distinguish 
the shell itself. The beds connected with and about the horizon of 
the Burdiehouse limestone are particularly noticeable for this. The 
like has also been pointed out by Messrs. Armstrong and Young, 
who in their Catalogue of Scotch Carboniferous Fossils say, “ Found 
adhering to plants and shells in many of the beds of the Upper Coal- 
measures.” * Now, the association of Microconchus (or Palcorbis) 
with bivalves in the place of plant-remains seems to me simply fatal 
to the view that the former is a terrestrial pulmonate Gasteropod. 
Allowing, for the sake of argument, that those found on fern fronds 
are Gasteropods of this nature, and had become accidentally immersed 
with the plants to which they were attached, how does this account 
for their appearance on the surface of bivalve mollusca in the same 
deposit, not only adhering, but also forming for themselves a similar 
depression or groove in the substance of the shells ? 
To the facts now adduced by me, it may be advanced that I am 
endeavouring to prove as of a freshwater habitat, an organism which, 
like the living Spirorbis, is of marine affinities. To this objection it 
may be replied—it is an incontestable fact that during the deposition 
of the Coal-measures, incursions of the sea did take place, consequent 
on a change of level, as shown by the occurrence of marine bands, 
such as the Pennystone Ironstone of Coalbrookdale;* the Gannister 
Coal, near Oldham;* and a band over the Great Mine Coal at 
Ashton-under-Lyne,® containing marine bivalves and Cephalopoda. 
During the deposition of the Wardie Shales precisely similar 
events took place. These beds are usually looked upon as of fresh- 
or brackish-water origin, but my own views have for a long time 
inclined much more to the brackish- than the fresh-water theory, 
after a prolonged and careful study of the organic remains found in 
them. Certain it is that definite and well-marked marine bands do 
occur, as, for instance, that at Woodhall, on the Water of Leith ; 
another at Craigleith Quarry, near Edinburgh ; another near Granton 
1 Mem. Lit Phil. Soc. Manchester, x. p. 196. 
2 Trans. Geol. Soc. Glasgow, iii App. p. 28. 
3 Prestwich, Trans. Geol. Soc. 1840, 2nd ser. v. p. 442. 
4 Mem. Geol. Survey of Gt. Brit. Country around Oldham, 1864, p. 62. 
5 Ibid. p. 64. 
