422 The History of Ichthyology 



Mrs. Rosa Smith Eigenmann, Dr. Joseph Swain, Wilbur Wilson 

 Thoburn (1859-99), Frank Cramer, Alvin Scale, Albert Jeffer- 

 son Woolman, Philip H. Kirsch (1860-1902), Cloudsley Rutter 

 (died 1903), Robert Edward Snodgrass, James Francis Abbott, 

 Arthur White Greeley, Edmund Heller, Henry Weed Fowler, 

 Keinosuke Otaki, Michitaro Sindo, and Richard Crittenden 

 McGregor. 



Other facts and conclusions of importance have been con- 

 tributed by various persons with whom ichthyology has been 

 an incident rather than a matter of central importance. 



The Fossil Fishes.* The study of fossil fishes was begun sys- 

 tematically during the first decades of the nineteenth century, 

 for it was then realized that of fossils of backboned animals, 

 fishes were the only ones which could be determined from early 

 Palaeozoic to recent horizons, and that from the diversity of 

 their forms they could serve as reliable indications of the age 

 of rocks. At a later time, when the evolution of vertebrates 

 began to be studied, fishes were examined with especial care 

 with a view of determining the ancestral line of the Amphibians. 

 The earliest work upon fossil fishes is, as one would naturally 

 expect, of a purely systematic value. Anatomical observa- 

 tions were scanty and crude, but as the material for study 

 increased, a more satisfactory knowledge was gained of the 

 structures of the various major groups of fishes; and finally 

 by a comparison of anatomical results important light came 

 to be thrown upon more fundamental problems. 



The study of fossil fishes can be divided for convenience 

 into three periods: (I) That which terminated in the mag- 

 num opus of Louis Agassiz; (II) that of the systematists whose 

 major works appeared between 1845 and the recent publica- 

 tion of the Catalogue of Fossil Fishes of the British Museum 

 (from this period date many important anatomical observa- 

 tions); and (III) that of morphological work, roughly from 

 1870 to the present. During this period detailed considera- 

 tion has been given to the phylogeny of special structures, 

 to the probable lines of descent of the groups of fossil fishes, 

 and to the relationships of terrestrial to aquatic vertebrates. 



* For these paragraphs on the history of the study of fossil fishes th< 

 writer is indebted to the kind interest of Professor Bashford Dean. 



