JURASSIC AND TRIASSIC BRACHIOPODA. 229 



CONCLUDING REMARKS. 



After three years of uninterrupted research devoted to the elaboration of this Jurassic 

 and Triassic Supplement, I have felt more and more the great difficulty in dealing with 

 species and their interminable variations. Certainly it saves much trouble to unite under 

 a single name, as some palaeontologists have done, a great many so termed species, 

 which other palaeontologists have considered to be distinct, but these combinations, often 

 judicious, have in many cases been the result of much guesswork, and not of positive 

 study, and thus, instead of clearing away confusion, have materially added to it. It is 

 decidedly wrong to burden the classification with an unnecessary number of specific 

 names for a thing that should have but one. The difficulty often is where to draw the 

 line. 



In this Supplement about 209 so-termed species and 30 named varieties have been 

 described and illustrated, namely, I species from the Rhastic formation, 87 species with 

 6 named varieties from the Lias, and 127 species with 24 named varieties from the 

 Oolites, 6 species being common to the Lias and the Oolites, but I feel convinced that 

 some years hence, when the subject shall have been still more studied than it has been 

 up to the present time, and with a still larger command of material, this number will 

 require to be largely reduced, for some of the so-termed species that swell up the 

 number are based on minute objects which may turn out to be the young of other 

 species, and some forms that are at present supposed to be distinct, will prove to be 

 mere variations in shape or varieties. Noting, therefore, these serious imperfections, 

 which I fear must inevitably accompany similar Monographs, I believe, nevertheless, that 

 the large bulk of the species described in this Supplement are good, as far as species go, 

 as they have been elaborated with the greatest possible care and attention. It has several 

 times been deemed preferable to give a provisional name to an uncertain form, rather than 

 to incorporate it with a good, well-defined species to which I did not feel certain it 

 belonged. 



The important and zealous help I have received, during the preparation of this 

 Supplement, from Messrs. J. F. Walker, C. Moore, E. Smithe, Buckman, Darell 

 Stephens, J. Prestwich, J. Parker, R. Etheridge, R. Tate, J. F. Blake, W. H. Hudleston, 

 T. Beesley, P. B. Brodie, J. W. Judd, J. Griffin, E. A. Walford, and others, sufficiently 

 attests the efforts that have been made to place before the Members of the Palaeonto- 

 graphical Society as complete a Monograph as the material at our command could 

 enable us to produce. I would, however, urgently recommend a further and continued 

 study of the subject, and a search for more specimens of those forms that are still 

 insufficiently [elaborated, by those who may be favourably located for similar investigations. 



If we briefly scan the results obtained as to the approximate number of species and 



