TRANSACTIONS OF WAGNER 

 1552 



TERTIARY FAUNA OF FLORIDA 



shall be required than are found in the contemporaneous faunas of the present 

 day in similar cases. This is undoubtedly true of the faunas treated of in this 

 Memoir. 



In the course of the work it became necessary to consider the systematic 

 arrangement of the pelecypoda. The general subject required revision in the 

 light of recent researches, both in anatomy and paleontology. With this view 

 Part III. was devoted to a compilation of existing data, in which material from 

 many sources was brought together and an approximate classification deduced. 

 This paper called attention to the subject, and one of the results was an investi- 

 gation by Dr. W. G. Ridewood, of the British Museum, into the characters of 

 the gills of this group of mollusks as a basis for their systematic arrangement. 

 This valuable piece of work * has corrected many errors and given much new 

 information based on modern methods of minute anatomical research. It is 

 obviously too soon to decide the general question upon which these observa- 

 tions bear, but, on the whole, from the writer's point of view, they rather sup- 

 port than weaken his previous conclusion that the gills are vmsuitable for use 

 as fundamental characters in systematic arrangement. 



The description of the several stages or horizons and lists of the species 

 recognized at each now follow. 



It will be observed that numerous undescribed species occur in parts of 

 these lists which have come to hand since the work was begun, but too late 

 to be included in the text. Also that some revision of the nomenclature has 

 been made, so that the lists are approximately up to date, comparable with 

 each other, and practically uniform in arrangement. 



These lists will be followed by a summary in tabular form showing the 

 relations of the faunas to one another and statistics j of the work covered by 

 the text. It may be mentioned that practically all the types of species de- 



* Phil. Trans. Royal Soc. Lond., Ser. B, vol. cxcv., pp. 147-284, 1903. 



t It may be of interest to note that during the progress of this work approximately 

 eight thousand three hundred and fifty species have been discussed or compared and 

 eight hundred and sixty new forms described. More than fifty new group-names, from 

 sections to genera, have been proposed and more than five times as many reduced to 

 the rank of synonyms as unnecessary or belated. The number of species known at 

 present between the beginning of the Oligocene and the present fauna is between three 

 and four thousand, probably less than half as many as will eventually be obtained and 

 discriminated. The lists here given have one rather exceptional advantage in that they 

 are all made by one person (the writer), and hence are more strictly comparable than 

 similar lists compiled, as is frequently the case, from diverse sources. 



