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| Keywords: The Quarterly journal of the Geological Society of London (13204922935).jpg ANNIVERSARY ADDRESS OF THE PRESIDENT 45 <br> Are there discernible in the members of these two orders such <br> structural resemblances as command our assent to their common <br> ancestry <br> Disregarding Placodas as too imperfectly known and limiting the <br> comparison to the elements of their shoulder-girdle and limbs or in <br> Prof Owen's words to their sterno-coraco-scapular frames and <br> limbs there are present in all the genera of each order in which <br> these parts are known two pairs of bones the essential nature and <br> identity of which are undoubted the coracoids and scapulae <br> Fig 1 ” Shoulder-girdle of Ichthyosaurus ventral view <br> ci the ciavicie; ic tiie interelavicle ; sc tiie scapula; cor the coracoid ; <br> gl the glenoid fossa <br> In Ichthyosaurus fig 1 the coracoids are relatively broad and they <br> are deeply notched in front and behind the glenoid fossa In the <br> typical Plesiosauri as P dolichodeirus fig 2 the coracoids are long <br> and narrow In Cope's subgenus Elasmosaurus as also in P Manseli <br> Hulke and Colyrnbosaurus Seeley which are evidently closely related <br> to it the bony coracoid is broad but of relatively small antero-posterior <br> extent and it sends backwards from the postero-external angle a <br> wing-like process or cartilage leaving a vacuity perhaps subtended <br> by membrane <br> In Nothosaurus a deep narrow notch separates a long square pro- <br> cess in front of and internal to the glenoid part of the bone which <br> a constriction divides from a large rhomboidal expansion that meets <br> the other coracoid in the middle line Yet under these diversities of <br> form the true homology of the coracoid is too plain to be missed ; and <br> this is equally true of the scapula to which I shall presently return <br> Ichthyosaurus our sole representative of the order Ichthyopterygia <br> has in its shoulder-girdle a third pair of bones by general consent <br> clavicles Are these bones present in the Plesiosaurian shoulder-girdle <br> and in that of the other genera of Sauropterygia Some anatomists <br> answer this affirmatively finding clavicles in Plesiosaurus fig 2 in <br> that piece which extends forwards and inwards from the glenoid part <br> of the scapula to the median azygos bone reputed episternum or inter- <br> clavicle and they consider that in this genus the clavicle is confluent 36929350 113681 51125 Page 45 Text 39 http //www biodiversitylibrary org/page/36929350 1883 Geological Society of London NameFound Colyrnbosaurus NameFound Elasmosaurus NameConfirmed Elasmosaurus EOLID 4532468 NameBankID 4153956 NameFound Ichthyosaurus NameConfirmed Ichthyosaurus EOLID 13226022 NameBankID 4204055 NameFound Nothosaurus NameConfirmed Nothosaurus EOLID 4532508 NameBankID 4260130 NameFound Placodus dolichodeirus NameConfirmed Placodus EOLID 4532601 NameBankID 4299008 NameFound Plesiosaurus NameConfirmed Plesiosaurus EOLID 4532515 NameBankID 4302234 NameFound Sauropterygia NameConfirmed Sauropterygia EOLID 4532436 Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 39 1883 Geology Periodicals Smithsonian Libraries bhl page 36929350 dc identifier http //biodiversitylibrary org/page/36929350 smithsonian libraries Information field Flickr posted date ISOdate 2014-03-16 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/13204922935 2015-08-26 12 55 39 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1883 Photos uploaded from Flickr by Fæ using a script | ||||
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