DEVONIC FISHES OF THE NEW YORK FORMATIONS 93 



Nor is there any sure foundation to the view adopted by Woodward, that 

 they are to be considered as armored offshoots of the Dipnoans. 



Again, at page 445 of the same volume, this passage occurs : 

 These creatures have been often called ganoids, but with the true 

 ganoids like the garpike they have seemingly nothing in common. They 

 are also different from the Ostracophores. To regard them with Wood- 

 ward as derived from ancestral Dipnoans is to give a possible guess as to 

 their origin, and a very unsatisfactory guess at that. 



Finally, reference may be made to two papers published lately by 

 the present writer,' in which he endeavored to show that the dentition of 

 Arthrodires belongs distinctly to the Dipnoan type, and that real homolo- 

 gies exist between their dermal cranial plates and those of the living Neo- 

 ceratodus. Indeed, the modern form was held to bear as intimate structural 

 resemblance to Coccosteans on the one hand, as to Ctenodipterines on the 

 other, although conforming more nearly than either in certain respects to 

 the hypothetical ancestor from which all three types — Ceratodonts, Arthro- 

 dires and Ctenodipterines — have been derived. 



The position maintained in this last communication is adhered to in 

 the present memoir, and it is believed that sufficient evidence has now been 

 accumulated to sustain its correctness. Heretofore, in default of positive 

 evidence, writers have been unable to demonstrate the truth of any one of 

 the various conjectures put forward to explain the nature of Arthrodires. 

 However plausible one or another of these may have appeared, however 

 widely they have gained acceptance, it must be remembered that a sug- 

 gestion remains a suggestion, and a hypothesis a hypothesis, until its cor- 

 rectness is fully demonstrated. Rightly is it said in one of Plato's Socratic 

 dialogues r"" "Mere beliefs or opinions are, like the statues of Daedalus, 

 runaway things ; not until they have been tied down by the chain of causal 

 sequence do they stand fast and become in the true sense knowledge." 



What constitutes this "reasoned interconnection" in the present case 

 may be told in few words. In the first place we must anticipate a little by 



^ Eastman, C. R. Dipnoan Affinities of Arthrodires. Am. Jour. Sci. ser. 4, 1906. 

 21:131-43. Idem. Mus. Comp. Zool. Bui. 1906. 50:1-30. 

 ^ Meno, 159 D. 



