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| Keywords: The Quarterly journal of the Geological Society of London (12711785514).jpg 48 <br> PROCEEDINGS OF THE GEOLOGICAL SOCIETY <br> The rim of this species and some others but not of all the Radio- <br> lites is marked vAth bifurcating impressions which radiate from the <br> inner to the outer margin fig 12 They owe their definition to a <br> change in the form of the cells <br> The inner layer of shell is often wanting being only indicated by a <br> space between the outer wall and the calcareous mould of the original <br> interior These moulds figs 15 16 called Birost rites by Defrance <br> have greatly puzzled naturalists especially when imperfect <br> In the British Museum there are several specimens of i calceo- <br> loides and R mamrnillaris in which the inner layer of shell is re- <br> placed by spar whilst the interior was filled with soft chalk and <br> allowing the separation and development of the valves <br> The interior of the lower valve of R mamrnillaris fig 10 exhibits <br> no inflections of the outer wall or only a slight ligamental ridge ; <br> the cartilage-pit is deep and furrowed and divided by an inflection <br> of the inner wall The dental pits are deep subequal and strongly <br> grooved The muscular impressions are shallow striated and nearly <br> equal <br> The interior of the upper valve figs 11 13 14 has an um- <br> bonal cavity turned towards the hinge and slightly mider-cutting it <br> In young specimens it is deep and conical but becomes shallow <br> or completely filled up with age The teeth are straight and pro- <br> minent fitting accurately the grooves in the sockets <br> Figs 13 14 ” Two side-views of the upper valve of Radiolites <br> mammillaris from the same specimen as Fig 1 1 <br> Fig 13 <br> Fig 14 <br> I <br> I ligamental inflection ; t t teeth ; a a' muscular processes <br> Each tooth supports a curved apophysis corresponding in form <br> to the muscular impressions in the lower valve In aged specimens <br> the apophyses nearly rest upon the impressions ; they are however <br> seldom so prominent as in this species f ” ' ' ' ' ' <br> There is no <br> longer <br> any <br> G Sowerby figured a Birostrites incequilobus in his Genera of SheDs ' and <br> rightly regarded it as the mould of a shell related to Diceras <br> t The specimen of R calceoloides in the British Museum like that described by <br> M Deshayes Bull Soc Geol France 2 ser viii 12 7 has lost almost all character <br> from its hinge as bivalves frequently do when aged 35614608 110213 51125 Page 48 Text v 11 http //www biodiversitylibrary org/page/35614608 1855 Geological Society of London NameFound Birostrites NameConfirmed Birostrites NameBankID 4091011 NameFound Deshayes NameFound Diceras NameConfirmed Diceras EOLID 13271618 NameBankID 2636432 NameFound R mamrnillaris NameFound Radiolites calceoloides NameFound Radiolites mammillaris Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 11 1855 Geology Periodicals Smithsonian Libraries bhl page 35614608 dc identifier http //biodiversitylibrary org/page/35614608 smithsonian libraries Information field Flickr posted date ISOdate 2014-02-23 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/12711785514 2015-08-26 20 55 58 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1855 Photos uploaded from Flickr by Fæ using a script | ||||
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