PREFACE. 



Of all the species composing the SUB-KINGDOM mollusca, none are, perhaps, 

 more varied, more elegant in their shapes, or more abundantly distributed, than those to 

 which the term Brachiopoda or Palliobranchiata has been applied : they are found in 

 the oldest deposits at present known to contain vestiges of animal life, and have continued 

 to exist, some in similar, but many under different shapes to the existing forms, through 

 the long successive periods which lead us to the present time. Their value to the 

 geologist is consequently very great ; and, as they so commonly fall under his hammer, 

 where other classes are often but sparingly represented, they must, therefore, be looked 

 upon as excellent data for the age of the deposit ; for, although some few individual forms 

 pass from one stage to the other, the generality are limited to defined horizons. The 

 study of so important an Order has, within the last fifteen or twenty years, particularly 

 interested the Palaeontologist who regarded something more than external shape. His 

 efforts, in this direction, have tended to acquire an intimate acquaintance with the 

 inhabitants of so remarkable a shell; and we have become more and more convinced 

 that to arrive at so desirable a knowledge, it was absolutely necessary to call upon 

 Zoology to point out, from a minute study of the animal, of the few species and genera 

 still existent, the use and origin of those remarkable calcified processes and varied 

 impressions visible in the numerous forms now extinct. 



Having devoted many years to the careful investigation of the subject under con- 

 sideration, and feeling desirous to contribute the little in my power to the advancement 

 of the views so laudably put forth by the Palseontographical Society, in 1849 I proposed 

 to the Council to do my best to prepare for them a general work on all the British 

 species of Brachiopoda hitherto discovered,^ arranged in seven distinct parts, which 



1 From being almost a stranger in the country at the period above mentioned, on account of a 

 residence of many years in different parts of the continent, I did not sufficiently estimate all the difficulties 

 I should have had to contend with in preparing so extensive and difficult a work entirely on British species. 

 I had not only to become acquainted with the local geologists and their collections, but also with a 



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