The Levenshiilme Limestones 297 



his "Silurian System," p. 84, as having been found atArdwick, 

 Manchester. Posidonomya and several other shells have been 

 found, but the names have not yet been settled. Fragments 

 of bone were seen in almost every block, as well as on the 

 surface, under the green marly coating, but fast to the blue 

 limestone. The fish remains are in the hands of Mr. J. W. 

 Davis, F.G.S., F.L.S., of Halifax, for identification. They 

 include ribs,teeth,spines,and scales, and will probably be found 

 to belong to the Megalichthys and Strepsodiis. Unfortunately 

 all these fish remains occur in detached fragments, owing to 

 the thinness and irregular composition of the blue limestone 

 in which they generally occur, the rock itself being frequently 

 not over an inch in thickness. Sometimes it varies in the 

 same slab from i inch to 4 inches in a foot length, and with 

 a most uneven, undulating surface. Thin sections of this 

 No. 6 group of limestones shew an amazing variety of 

 organic remains. Firstly, they are crowded with fragments 

 of the shells of molluscs, intermingled with the more 

 delicate shells of crustaceans, and with spines, bones, and 

 other fragments of fishes in profusion. The small organisms 

 which fill up the field of view are of a blue grey colour, and 

 amongst them, cris-cross, are bones of a reddish brown 

 colour. The J^in. power gives the cellular substance of 

 these small bones perfectly. They belong to tiny fish, which 

 probably fed upon the Entomostraca, and whose presence 

 attracted the larger fishes, which in turn preyed upon them. 

 The identification of some basis, from which the true 

 position of the Ardwick limestone beds can be ascertained, 

 with reference to the Levenshulme series, has had our careful 

 attention. We have come to the conclusion that the 

 Ardwick bed, which contained the remains oiih^ Megalichthys 

 Hibbertii, is the same as this No. 6 Group. It is a very 

 marked and peculiar bed, consisting of two colours, the 

 pink containing Spirorbis^ and the blue containing shells of 

 the Anthracomya. The fossils of the Ardwick limestone 

 S 



