398 GENERAL SUMMARY TO 



competent palaeontologists ; for I feel certain that what has been found to be the case 

 with reference to the passage of the same species from the Upper Tertiary into the Recent 

 epoch will apply equally so to many species that occur in other consecutive formations. 

 The resemblance, for example, between the recent Mhynchonella nigricans and some 

 Cretaceous and Jurassic forms is so great that we are at a loss to define their 

 differences. Some Lingulce and other forms offer the same striking resemblances. 



In this Monograph all the so-termed species of British Fossil Brachiopoda that 

 have been discovered up to the end of 18S3 have been described and illustrated. 

 I am, however, perfectly certain that much more will require to be done before 

 it will be possible to ascertain with any degree of certainty what is even the approxi- 

 mate numbers of really good British species, what are their synonyms, and what 

 variations in shape, and varieties are assumed by each species. A large number of the 

 so-termed species will, with further study, be found to be linked by transitional or passage 

 forms, provided a sufficient number of specimens be collected and compared ; and the 

 subject relating to lateral variation is one which must be minutely and carefully inves- 

 tigated by future palaeontologists. The internal details of each species should be sought 

 for, carefully described, and illustrated ; and from time to time supplements should be 

 prepared and published in the volumes of the Palaeontographical Society until the time 

 has come for the preparation and publication of a new general work on British Eossil 

 Brachiopoda, a work that will be surely needed some years hence. 



I have done my best, and am fully aware of the many shortcomings in my work, but 

 must now leave the task to be pursued and accomplished by younger and more able 

 hands. 



In order to hope to reach a really comprehensive idea as to the number of good 

 species referable to the same genus as occurring all over the world, some one should take 

 up a large family at a time, assemble all obtainable material, class, describe, and figure 

 all the species side by side, and trace their passages one with the other. Had my life 

 not been so far advanced I would, for example, have liked nothing better than to have 

 prepared a general monograph of all the known Tretenterata. 



The subject embracing the whole Brachiopoda has become so vast that it is almost 

 hopeless for one person to be able to deal with it in its entirety ; but taken in 

 parts it can be easily accomplished, and this would advance our knowledge very con- 

 siderably. Fifty years, as is justly observed by the Duke of Argyll in his Address to the 

 Geological Society of Edinburgh on the occasion of its fiftieth anniversary in 1883, "is 

 but a fragment of time in the history of many sciences, but is a whole age to ours." 

 We may truly assert that during the last half century has been firmly laid clown the 



