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| Keywords: The Quarterly journal of the Geological Society of London (13205961024).jpg 80 <br> PROCEEDINGS OF THE GEOLOGICAL SOCIEEY DeC 2 <br> judging from their present forms they appear shortened at least <br> twenty-five per cent in a direction perpendicular to the strike of <br> the cleavage across the bed <br> Fig 3 <br> Similar instances are common where flat shells are found in slaty <br> beds the large Posidonise in the black shale above the limestones <br> at the base of the culm-series of Devonshire are frequently distorted <br> in the same manner ; at the limestone quarry of Bickington one <br> mile and a half south of Barnstaple thousands may be seen in the <br> shale thrown off the top of the quarry every one of which is con- <br> tracted in a direction perpendicular to the line of strike of the cleavage <br> across the bed and which are all covered with folds parallel to that <br> line The cleavage intersects the bedding at an angle of about 50° <br> The case of the Trilobites in the Llandeilo flags mentioned by Pro- <br> fessor Phillips in the passage already quoted is analogous to these <br> In all these cases the shells appear to have suflTered from lateral <br> pressure which has altered their forms and produced the parallel folds <br> on their surface <br> Fig 4 <br> The same lateral pressure has produced a different effect on gibbous <br> shells which are usually flattened in a direction perpendicular to the <br> cleavage and drawn out or squeezed out considerably in the diiection <br> of the dip of the cleavage planes The result is seen in the Spirifer <br> disjunctus represented in figs 4- and 5 from one of the slaty beds at <br> South Petherwin met by the cleavage at an angle of about 60 <br> Figure 4 Shows the shell as it lies on the bed its length reduced <br> about one-half from A to B by compression perpendicular to the <br> cleavage planes the strike of which across the bed is shown as usual 36932809 113687 51125 Page 80 Text v 3 http //www biodiversitylibrary org/page/36932809 1847 Geological Society of London NameFound Spirifer disjunctus NameConfirmed Spirifer disjunctus Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 3 1847 Geology Periodicals Smithsonian Libraries bhl page 36932809 dc identifier http //biodiversitylibrary org/page/36932809 smithsonian libraries Information field Flickr posted date ISOdate 2014-03-17 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/13205961024 2015-08-26 12 53 24 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1847 Photos uploaded from Flickr by Fæ using a script | ||||
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