THE BRITISH FOSSIL BRACHIOPODA. 



3S3 



modifications in shape assumed by individuals of a single species which are so commonly 

 found in the same bed or sea-bottom and confounded with real varieties. 



Science progresses step by step, and I consider that what has been achieved during 

 the last forty years is ample encouragement to prosecute investigations, so as to be able, 

 with time and patience, to arrive at something really definite and satisfactory. A species 

 cannot be properly understood, described, and illustrated by the simple inspection of one 

 or two examples ; a great many are required, especially at different stages of develop- 

 ment, in order to ascertain its modifications in shape and character. The interior and 

 the shell-structure must also be carefully examined and illustrated. The admirable 

 results attained, but not until after much time and repeated trials, by the Rev. Norman 

 Glass, Prof. J. Hall, Mr. Whitfield, Herr Zugmayer, Dr. Waagen, and some others, have 

 amply proved that where there is a will there is a way, and that the hardest matrix can 

 be removed from the interior of the fossil shell so as to expose its internal details and 

 characters. 



At different periods efforts have been made to draw up catalogues of the described 

 species. Bronn, in his 'Index Palaeontologicus,' 1848, gives a list of all the species 

 known to him to have been described up to that year. Morris, in 1843 and 1854, 

 published a catalogue of the then known British species. A. d'Orbigny, in 1849, 

 gave in his ' Prodrome ' a very incomplete catalogue of the Brachiopoda. S. A. Miller, 

 in 1877, issued a catalogue of American Palaeozoic fossils. Catalogues of the Silurian, 

 Devonian, and Carboniferous species were published by the late Dr. Bigsby in his 

 'Thesaurus Siluricus' (1868) and' Thesaurus Devonico-Carboniferus ' (1878). But all 

 these catalogues are compilations of so many so-termed species, without any really critical 

 comparison (except in the case of Morris's ' Catalogue '), and serve as works of reference 

 and not to indicate the real number of good species. 



Dr. Bigsby informed me some time previous to his death that, from a conspectus of 

 his two ' Thesauri,' the following numbers of Silurian, Devonian, and Carboniferous 

 Brachiopoda had been arrived at with due regard to accuracy, but after all only forming 

 a careful approximation, liable to future disturbances. 





American. 



European. 



Total. 





689 

 577 



488 



733 

 789 

 384 



1422 

 1366 

 871 











1754 



1906 



3659 



The number from the Permian formation, which completes the Palaeozoic series, has 

 not yet been computed, but it is comparatively small. Making a large allowance for 

 synonyms, it will be seen that some 3000 so-termed species of Dr. Bigsby's list had up to 



