GEOLOGY 



The Middle Measures of the Bolton, Oldham, and Rochdale districts have yielded a number 

 of rare and mteresting crustaceans ; and work which is now being carried on at Sparth Bottoms 

 near Rochdale in shales over the Arley Mine bids fair to reveal many new forms. 



Fossil fishes are represented by large spines, teeth, scales, and not rarely by whole fishes. Seven 

 species of Pleuracanthian spines are known, the commonest being Pleuracanthus lavisnmus. All 

 these spmes consist of a stout bony rod which was imbedded in the body muscles of the fish, either 

 behmd the head, or in front of each of the paired fins. The hinder surface of each spine is armed 

 with small acutely pointed denticles arranged in two or even more rows. Larger and stouter spines, 

 often a foot in length, and ornamented by oblique rows, or tubercles, have received the name 

 of Gyracanthus, whilst spines ornamented by longitudinal ridges are known as Sphenacanthus. Many 

 of the Lower Coal Measure fishes continue to exist, and the black shales forming the roof of several 

 of the thick coal seams are veritable storehouses of fish remains. Amphibia are not satisfactorily 

 represented, although certain large ring vertebrae and small ribs are known and doubtfully referred 

 to Archegosaurus. 



UPPER COAL MEASURE FAUNA 



As already stated, the fossils found here are scanty and small. The period was one in which 

 extinction was going on. 



Spirorbis pusUlus, and ostracods, the latter of several species, alone seemed to have flourished 

 in anything like numbers, whilst Anthracomya Phillipsii, and A. /avis var. Scotica are the only 

 common forms amongst the mollusca. Arthropods are represented by Estheria tenella, and Leaia 

 Leidyi var. Williamsoniana. The fishes were mainly Pleuracanthus, Gyracanthus, Ctenodus Murchisoni, 

 and Megalichthys Hihherti, a typical Middle Measure form. Small phalanges referred to Laby- 

 rinthodon were found by Mr. Chas. Roeder at Longsight and are the only remains of amphibia 

 known from these beds. 



PERMIAN 



Strata belonging to this period formerly occupied a much greater area in the county than now, 

 the formation having been extensively swept away by post-Permian denudation, which was possibly 

 rendered more effective by a considerable amount of earth movement, such as faulting. (See p. 20.) 

 Much of the existing Permian strata is covered by the Trias or Glacial Drift, so that the only 

 portions readily accessible are small and comparatively unimportant. A narrow band of Red Sand- 

 stones, Marls, and Limestones borders the South Lancashire Coalfield from Sutton near St. Helens, 

 Edge Green, Leigh, and Astley to Eccles. At the latter place, and again at Salford and Cheetham 

 Hill, the formation has been faulted northwards by the Great Irwell Valley and other faults, which 

 here traverse the coalfield. The fact that the Permian has shared in the movement and faulting of 

 the coal measures indicates that the latter movements took place after the deposition of Permian 

 and not before. 



The Red Sandstones, Marls, and Limestones are best seen on the east side of Manchester 

 from CoUyhurst to Stockport. They were also cut through in the making of the Fallowfield 

 and Burnage section of railway on the east of Manchester, where their junction with the Coal 

 Measures below could also be seen. Small patches of the Permian sandstones occur west of Preston, 

 on the banks of the Ribble near Clitheroe, on the Ingleton Coalfield, and in the Furness district. At 

 this latter place the beds are much obscured by drift. 



The position of the Permian has been determined in a number of cases by means of borings 

 made in search of iron ore. The Red Sandstones are seen at High Cocken, north of Barrow, and 

 quarried at Hawcoat, whilst old quarries opened in the same rock exist in the grounds of Furness 

 Abbey. The Magnesian Limestone which underlies the sandstone is also present in the Furness 

 district, and has been worked at Old Holebeck. The smaller patches which occur near 

 Clitheroe and elsewhere owe their preservation to their position on the downthrow side of faults. 

 They are outliers of the great mass of Permian strata which formerly existed. 



Fossils are poorly preserved in the Permian sandstones and marls, the latter yielding at various 

 places examples of Schizodus and Bakevellia, whilst the thin limestones are at times crowded with 

 species of Rissoa, Turbo, etc. Polyzoa are not unfrequent in the Magnesian Limestone. 



The Permian System as a whole consists of the following divisions : — 



Upper Red Sandstones, Marls, and Clays, with thin limestone. 



Magnesian Limestone. 



Marl Slate. 



Lower Red variegated Sandstones, Marls, and Breccias. 



Only the Upper Red Sandstone and Magnesian Limestone are exposed in the county. 



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