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| Keywords: The Quarterly journal of the Geological Society of London (12960559534).jpg 328 J W DAYIS ON THE GENUS PLEUKACANTHUS AGASS <br> Fig 4 Pleurcicanthus pidchellus Davis <br> Denticles of spine enlarged <br> quently crushed ; the upper two thirds of the length are armed on <br> each lateral face with about twenty exquisitely beautiful little <br> denticles ; they are firmly attached recurved towards the base and <br> culminate in an acute point fig 4 <br> The beauty of this little ichthyodorulite has suggested its specific <br> name <br> Locality Cannel Coal Tingley M CM <br> It is possible that the small spine P pulcTiellus may be the <br> immature form of some other species ; but I have at present no evi- <br> dence that such is the case I have in all half a dozen specimens ; <br> and they are all of the same size within the eighth of an inch It <br> most resembles P Icevissimus Ag There is a considerable simi- <br> larity in the denticulation of this form and the type of Agassiz ; at <br> the same time the method of insertion in the mass of the spine is <br> different If these were young and immature specimens we ought <br> also to find them of other and intermediate sizes ; but hitherto such <br> has not been the case It is possible that further evidence may be <br> found ; but for the present it will be better to distinguish these <br> spines as a distinct species <br> 5 Pleuracanthtjs alteenidentatfs sp nov PI XII fig 3 <br> Spine straight 2 5 inches in length when perfect '2 inch in <br> greatest diameter at the base Prom the base the diameter of the <br> spine decreases until it ends in a blunt point ; the internal cavity is <br> terminal circular and comparatively small ; external surface striated <br> longitudinally ; anterior and lateral faces circular in section ; the <br> posterior depressed and about the width of the diameter of the spine <br> fig 5 <br> Pig 5 PleuracaniJms alternidentatus Davis <br> M <br> Section of spine nat size <br> The angle formed by the junction of the lateral and posterior faces <br> is set with seven or eight widely separated obtuse denticles ex- <br> tending from the apex along one third of the length of the spine <br> They present the peculiarity of being inserted alternately the <br> denticle of one side being opposite to the depression on the other <br> Prom this characteristic I have applied the nomen triviale as above <br> Locality Coal-measures Middleton near Leeds Leeds Literary <br> and Philosophical Society's Museum 36090687 111264 51125 Page 328 Text 36 http //www biodiversitylibrary org/page/36090687 1880 Geological Society of London NameFound Pleuracanthtjs alteenidentatfs sp NameFound Pleurcicanthus pidchellus Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 36 1880 Geology Periodicals Smithsonian Libraries bhl page 36090687 dc identifier http //biodiversitylibrary org/page/36090687 smithsonian libraries Information field Flickr posted date ISOdate 2014-03-06 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/12960559534 2015-08-26 15 54 01 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1880 Photos uploaded from Flickr by FĂŚ using a script | ||||
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