6 INFERIOR OOLITE AMMONITES. 



which these thirteen represented, is found to have been described in this Monograph 

 in about 450 species, distributed among some 75 genera. 



These comparisons may give some idea of what has to be done to complete the 

 work. If the three of the Sowerbys have become 450, then their fifteen, which 

 belong to series untouched by the present portion of the work, might be expected 

 to produce five times as many. However, this proportion is too high. The 

 proportion in Morris is thirteen to twenty ; and that seems to agree with what is 

 known of the undescribed portion of the fauna. Therefore, there are rather more 

 than as many species again to be described before the British Inferior Oolite 

 Ammonites are anything like completely known. 



The many years over which the appearance of the parts of the work has been 

 spread, ought to be taken in account in any judgment on the work as a whole. 

 The work should be regarded as an example of the evolution of ideas concerning 

 the fauna and the strata whence the fauna has come. During all these years the 

 author has been the learner carrying on researches ; and, as those researches 

 became more and more complete, they showed the necessity for greater discrimina- 

 tion with regard to the names of strata and of species. This has involved many 

 alterations in names, which are to be found in the Supplement. Therefore, the 

 reader will do well to study the Supplement first, and to interpret the early parts 

 of the work by means of the Supplement. This Supplement may be said to 

 represent the author's mature conclusions as to the classification and nomenclature 

 of the species and the strata in which they occur — conclusions arrived at through 

 researches carried on while the Monograph was in progress. 



Perhaps the volume would have been more consistent had the publication of 

 the earlier parts been delayed until these researches were more complete ; but, on 

 the other hand, it is certain that these researches were carried out just because of 

 the incentive which the publication of the Monograph gave : lacking that, they 

 might not yet have been undertaken by the author, faced by a constant struggle 

 with ill-health and anxiety. 



To many fellow-workers the author desires to express his very great indebted- 

 ness. To the late Prof. Alpheus Hyatt and to Prof. Emile Haug he is very 

 particularly indebted — the views of the former upon tachygenesis, and those of 

 the latter upon convergence have had very much influence upon the system of 

 classification now adopted. To these authors he also desires to express his best 

 thanks for the kind presentation of their works ; while for similar welcome and 

 important additions to his library he owes hearty thanks to Prof. Guido Bonarelli ; 

 Dr. L. Brasil; Profs. W. Branco, E. W. Benecke, M. Canavari; Dr. Paul Choffat, 

 Dr. A. Denckmann; Prof. G. Gemmellaro ; Dr. G. Geyer; Profs. W. Kilian, G. 

 Meneghini, E. Mojsisovics, C. F. Parona, A. Pavlow, J. F. Pompeckj ; Dr. J. 

 Siemiradzki, Dr. J. P. Smith, Dr. M. Vacek ; Prof. F. Wakner ; and to so many 



