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| Keywords: The Quarterly journal of the Geological Society of London (12960266133).jpg J W DAVIS OH- THE GENUS PLETJRA CANTHUS AGASS 325 <br> Tie considers may have served a similar purpose to that of the claspers <br> in cartilaginous fishes or the sheat-fishes In some specimens they <br> are absent ; and these he concludes were female fishes <br> The zoological affinities of this genus have been the subject of <br> much careful research Prof Agassiz considered it as representing <br> – a fossil Eay nearly related to Trygon Dr Goldfuss consigned <br> the genus to the Selachians from its resemblance to Squatina and <br> more recently Dr Kner has contended that it constitutes a distinct <br> order between the Selachians and the Teleosteans having many <br> features in common with each and forming an intermediate link <br> hetween the cartilaginous and bony fishes <br> Pletjeacanthus Agassiz Davis <br> Sjnnes more or less circular in section with an internal cavity <br> ˘terminal at the basal extremity extending towards the apex ; straight <br> or slightly curved and gradually tapering to a point ; surface of the <br> spine where not denticulated smooth or finely striated Implanted <br> portion of base short with thinner walls than the exposed part of <br> the spine Along some part of the surface there extend two rows of <br> denticles ; these may be widely separated and lateral they may ex- <br> tend in close proximity along the posterior surface of the spine or <br> the two rows may occupy any intermediate position between the two <br> - specified <br> 1 Pleuracanthus LJ2VISSIMTJS Agass Fig 1 <br> S2nne 8 or 9 inches long -6 to 8 of an inch in largest <br> diameter at the base tapering evenly to a fine point Straight oval <br> In section with an internal cavity extending from the base to within <br> a short distance of the point Anterior and posterior faces smooth <br> or finely striated ; their lateral junctions are armed with a row of <br> acuminate denticles fig 1 strongly curved towards the base with an <br> Fig 1 ” Pleuracanihus Icevissimus Ag <br> Denticles of spine enlarged <br> inclination towards the posterior face of the spine Each denticle <br> occupies about -1 of an inch Near the point they are smaller and <br> at the opposite cxtremit - somewhat larger They extend from the <br> point along two thirds the length of the spine <br> M Agassiz who described this genus and species from an imper- <br> fect specimen obtained from the coal-shales near Dudley lays con- 36090684 111264 51125 Page 325 Text 36 http //www biodiversitylibrary org/page/36090684 1880 Geological Society of London NameFound Pletjeacanthus NameFound Pleuracanihus NameFound Pleuracanthus NameConfirmed Pleuracanthus EOLID 20530464 NameBankID 2879732 NameFound Squatina NameConfirmed Squatina EOLID 11117537 NameBankID 2485681 NameFound Trygon NameConfirmed Trygon EOLID 4536889 NameBankID 2535591 Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 36 1880 Geology Periodicals Smithsonian Libraries bhl page 36090684 dc identifier http //biodiversitylibrary org/page/36090684 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 N02/12960266133 2015-08-26 15 51 48 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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