232 SUPPLEMENT TO THE 



these I have been able to put right in the Supplement, but many will still require to 

 be corrected by future palajontologists as science progi'esses and our knowledge becomes 

 extended. 



A large proportion of our species have certainly been thoroughly worked out, all 

 their external characters and internal details having been completely elaborated ; but 

 many so-termed species cannot yet claim that advantage, and their generic and specific 

 characters have still to be precisely determined. Many of them, when better understood, 

 will, no doubt, have to be considered as synonyms of some of those that have been fully 

 described ; but many years must necessary elapse before it will be possible to offer a 

 definite list of our species. Every form that can be thoroughly made out, described, and 

 illustrated is positive gain to science. It is wrong to burden science with specific names 

 that are not absolutely necessary ; and it is equally wrong to combine under a single name 

 forms that are in reality specifically distinct. 



I shall add one part more to this volume, in order to sum up general results, and to 

 give a catalogue of the species described in this and the previous four volumes, as 

 well as a Brachiopodal bibliography. 



It now remains for me once again to express my grateful thanks to the many British 

 and Foreign scientific friends who have afforded me valuable and valued help during the 

 progress of my lengthened investigations. 



