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ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1934 



From the time of the classic investigations by Kovalevski and 

 especially by Dollo, there have been attempts in paleontology to 

 introduce a more biological method of investigation. That is to say, 

 workers have not been content with giving merely a description of 



FiGDRE 1. — Systematic subdivisions of fishlike forms and fishes based upon ttie recent 

 investigations. Agnatiis, the forms without jaws, comprising only one class — the Ostra- 

 coderms. Gnathostoms, or forms with true jaws, comprising in addition to the fishes 

 all other vertebrates (amphibians, reptiles, birds, and mammals). According to 

 Stenslo's Investigations the Placoderms must be regarded as belonging to the Elasmo- 

 branchs. (Modified after Gross.) 



