352 Ml*. J. Phillips on the Lower or Canister 



which in fact is the same thing as the " crowstone" of the 

 mountain limestone district in the north-west of Yorkshire, 

 and like that contains in abundance the remains of plants, 

 particularly of the genus Stigmaria, Brongn. By the extreme 

 abundance of plants of this kind, indeed, the galliard beds 

 may almost alwa\'s be recognised throughout their range in 

 Yorkshire. This stone, in some cases, forms the floor or sill 

 of the coal seams, — a circumstance never observed in the upper 

 coal strata, amongst which, indeed, galliard never occurs in 

 its true character. Hence this whole group of strata may be 

 appropriately called the Galliard or Canister coal series. 



The Ammonites and Pectens which lie above one of the 

 seams of coal, and still more the Ortlwcerce which sometimes 

 accompany them, are remarkably analogous to fossils of the 

 mountain limestone. The galliard is likewise to be compared 

 with similar stones in the mountain limestone series, and 

 therefore the ganister coal series might without impropriety 

 be associated with the upper-mountain-limestone series of 

 the Penine chain, or with the millstone grit and limestone 

 shale of Derbyshire, and thus the flagstone of EUand would 

 appear to be the lower limit of the true coal-measures. But 

 a short examination of the neighbourhood of Halifax, in Oc- 

 tober 1831, has shown me another order of phaenomena and 

 another set of shells, which connect this same series with the 

 upper or true coal-measures. 



In the upper coal series of Northumberland, Durham, York- 

 shire, and Derbyshire, are several most extensive layers of 

 bivalve shells, commonly called Muscle bands, and referred to 

 the genus Unio, from which the fresh-water origin of those 

 coal deposits has been inferred. It was therefore with extreme 

 gratification that I found, in passing through Mr. Kawson's 

 colliery at Swan Banks, in the midst of this series of ganister 

 coals, two layers of these shells, one of them about the middle 

 of the series, considerably above the Pccten coal, the other near 

 the bottom, and considerably below that coal. 



No shells of this kind have ever been met with in the moun- 

 tain limestone group, which there is every reason to consider 

 as of decidedly marine origin ; — not one of all the zoophytic, 

 testaceous, or crustaceous reliquiae of this limestone has ever 

 been found in the upper coal series : this opposition of zoo- 

 logical characters would appear to be fully explained, if the 

 coal deposits were admitted to have been accumulated in fresh 

 water, and this opinion is, perhaps, generally adopted. 



We find, then, in the lowest coal series, which is placed on 

 the line of transition between the marine and fresh-water de- 



