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| Keywords: The Quarterly journal of the Geological Society of London (12960278843).jpg J W DAVIS ON THE GENUS PIEIJEACANIHTJS AG ASS 329 <br> P aUernidentatus is more nearly related to P alatus than to any- <br> other It is however easily distinguished by its more robust ap- <br> pearance the diameter being greatest between the anterior and pos- <br> terior surfaces whilst in P alatus the transverse diameter is greater <br> The walls of the spine in this species are much thicker and stronger <br> than in P alatus The point of most divergence consists perhaps in <br> the widely separated and alternate denticles <br> 6 Pleueacanthus planus Agass sp indet <br> In the 'Poissons Fossiles ' tome iii p 176 M Agassiz records a <br> spine of Pleura canthus to which he has appended the specific name <br> planus ; it is said to be from the Coal at Leeds Sir Philip Egerton <br> who possesses the type of P planus writes me that it is about J <br> an inch in length the basal end being absent ; there are six or seven <br> strong booklets on each side imbedded in the matrix The exposed <br> surface is quite smooth and flat <br> 7 Pletjracanthtjs alatus sp nov PI XII fig 4 <br> Spine Length 2 2 inches breadth '2 inch ; the general form is <br> straight A slight appearance of curvature is given by the anterior <br> face curving from the base to the apex whilst the posterior is <br> straight From the basal end to the middle the spine has been <br> crushed ; it appears to have been uniform in diameter ; from mid- <br> length to the apex it becomes gradually smaller and ends in a fine <br> point It is uniformly striated on the anterior and posterior sur- <br> faces ; the intermediate furrows are frequently broken into a suc- <br> cession of pittings especially the lower parts There is an internal <br> Pig 6 ” PleuracantJius alatus Davis <br> a Section of spine nat size b Denticles much enlarged <br> -cavity open and large at the base In section the posterior face <br> forms a much-depressed curve the anterior curvature forming a semi- <br> circle above it fig 6 a ; the lateral angles formed by the junction <br> of the two are ornamented or armed with a row of denticles fig 6 b <br> numbering ten on each side They extend from the point -8 of an <br> inch The denticles are broad at the base closely set and short <br> terminating obtusely with a slightly trenchant edge parallel to their <br> longitudinal axis Those nearest the apex of the spine are less pro- <br> duced than those lower down <br> Locality Cannel Coal Tingley M CM 36090688 111264 51125 Page 329 Text 36 http //www biodiversitylibrary org/page/36090688 1880 Geological Society of London NameFound P alatus NameFound P planus NameFound Pletjracanthtjs alatus sp NameFound Pleueacanthus planus NameFound Pleura canthus Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 36 1880 Geology Periodicals Smithsonian Libraries bhl page 36090688 dc identifier http //biodiversitylibrary org/page/36090688 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 N02/12960278843 2015-08-26 15 56 42 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1880 Photos uploaded from Flickr by Fæ using a script | ||||
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