PREFACE. 17 



Heretofore these fields have been far too widely separated ; 

 and the work of the one has been carried on practically inde- 

 pendently of the other, with often very erroneous conclusions. 



During the past few years several hundred "new" species 

 and a considerable number of genera have been described from 

 that the upper Paleozoic rocks of Missouri. And it is safe to say 

 more than two-thirds of this number have unquestionably been 

 brought to notice before. Many of them are the commonest 

 species, described and well illustrated years ago. The folly of 

 such careless multiplication of names is only too apparent, and 

 certainly needs severe condemnation. The manifest indisposi- 

 tion to look up the readily accessible literature also reflects 

 sadly on the methods of the worker. At best, synonymy is 

 ever in great danger of unnecessary augmentation, and always 

 will receive sufficient additions without the wholesale, useless 

 allotments that need not be mentioned. Only when it is im- 

 possible to refer forms to species already described does it 

 become necessary, or desirable, to propose new titles. And in 

 all cases considerable familiarity with the representative spe- 

 cies is at all times helpful. Within the last decade the trend 

 of paleontological thought has been toward the higher ends 

 previously alluded to. Comparatively few new species have been 

 made known of late, indicating clearly that the day of indis- 

 criminate species-making is drawing rapidly to a close, and that 

 the efforts of paleontologists are being directed into the more 

 important channels, in ways more intrinsically valuable and 

 more in harmony with the truly philosophic spirit of pure 

 science. Thus it is that students, in dealing with problems 

 pertaining to ancient life, have begun to appreciate more fully 

 the direct bearing and close relations of this science to those 

 branches treating of the structure of animals, and their distri- 

 bution in time and space. 



The treatment of the different zoological groups referred 

 to in the present connection has not been the same. In order 

 to carry out the main intent of the work, and still have it 

 included within the limits originally planned, it has been neces- 

 sary to condense greatly the consideration of many of the sec- 



