THE GEOLOGIST 



AUGUST, 1858. 



OX EHYXCHOXELLA ACUTA AST) ITS ATTDsITIES. 



By JoHX Jo^-ES, Esq., Gloucester. 



0^^: of tlie most remarkable fossils assumed to be distinctive of a 

 particular geological horizon, and wkich., from its very striking out- 

 line, most readily impresses itself upon the mind, is the RhynchomUa 

 acuta of the Lias-marlstone, a Brachiopodous shell common at 

 Stinchcombe, Churchdown, and other localities of this district, and 

 well knoTvn elsewhere. Having paid considerable attention to the 

 class to which it belongs, I have long abandoned the common practice 

 of placing in the cabinet only those specimens which chance to 

 accord with the forms figured and described as typical. Instead of 

 doing this, I have selected, as good examples, those which manifestly 

 have not been crushed or injured prior to their entombment and 

 petrifaction ; and these I have arranged in series illustrative of specific 

 development. 



This mode of procediu'e has taught me that the species under 

 consideration assumes forms varying from that under which it is most 

 •generally known ; and it has led me to believe that several so-called 

 species of various authors are, in reality, mere varieties of this. 



All who have attentively studied the numerous TerebratulidEe of 

 the Cotteswolds will have experienced the difficulty of assigning 

 satisfactorily certain anomalous forms, occurring in beds ranging 

 vertically from the Pisolite, or even lower, to the Cornbrasli, to such 

 well-established species as Terehro.tuJa maxUJata, T. perornJU^ T. 

 glohata, or T. intermedia, and will remember the remarkable 

 varieties of individual character presented by other species, as, 

 for example, T. jjJicata, T. sim:£Ae:c^ T. nmhria, and T. carinata, 

 sufficiently strildng when studied in solitary examples, but, in an 



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