16 BIOLOGICAL SOCIETY OF WASHINGTON. 



The instances which I have mentioned, besides many others 

 which might be referred to, show that the confidence with which 

 many paleontologists have decided upon the question of the syn- 

 chronism of formations in widely separated portions of the earth, 

 some of which are at most only one or two hundred feet in thick- 

 ness, is quite unjustifiable. 



I would gladly end here my arraignment of the unwarrantable 

 positions which paleontologists have hitherto assumed, but I 

 have vet to refer to others, especially to the custom of deciding 

 upon the homotaxial relationship, or so-called equivalency, of 

 formations upon insufficient evidence. Before the student of 

 living animals and plants is prepared to decide in a satisfactory 

 manner upon the forms which he is investigating, he requires not 

 only a series of perfect specimens of his species, but also all that 

 can be known of its anatomy and physiology, its habits and 

 habitat, its associated forms, and its specific and generic rela- 

 tions. On the contrary, the paleontologist, as is well known, is 

 confined to the study of such of the hard or skeletal parts of 

 animals as may have escaped destruction by decomposition or 

 other means ; and the imprints or fragments of plants, mainly 

 leaves. 



One cannot cease to wonder at and admire the large amount 

 of real knowledge which has been gained by the study of even 

 such imperfect material as this. In fact, all that we know of the 

 ancient life of the earth has been derived from this source ; and 

 by means of comparisons with related living forms we are often 

 able, by the aid of a perfectly legitimate use of the imagination, 

 to restore to a large extent the faunas and floras of long past 

 geological periods. Encouraged by this success, and urged by 

 the necessities of geology, paleontologists have assumed not 

 only to decide upon the specific and generic identity of the forms 

 represented by such imperfect material, but also to base upon it 

 generalizations of the greatest importance in both geology and 

 biology. 



