DEVONIC FISHES OF THE NEW YORK FORMATIONS IO5 



date their significance, and to draw from them generalizations. Intolerably- 

 barren must be those lines of inquiry which result in no broad conclusions. 

 Natural science, however, and especially paleontology, imposes upon us this 

 difficulty : for an hour or two of synthesis, years of patient application in 

 the study of facts are required. 



That which has hitherto been puzzling in Macropetalichthys and Aste- 

 rosteus is the absence of a standard of comparison or other clues by means 

 of which their characters acquire significance ; they must needs remain 

 unintelligible until brought into adjustment with other definitely known 

 facts. Newberry, as we have seen, went widely astray in imagining these 

 forms to be ancestral to modern sturgeons. Cope's keen insight led him 

 immediately to perceive the resemblances between Macropetalichthys and 

 Dinichthys ; and in suggesting a comparison between the former and 

 Neoceratodus, he actually hit upon — though without adequately realizing 

 it — a. solution of the whole matter. Holding within his grasp the key to a 

 correct interpretation of the Arthrodiran skull in all particulars, one regrets 

 that he did not consistently apply it, instead of attempting vainly to estab- 

 lish homologies with the skull of Stegocephalians. Only in one respect 

 does he point out similarity of structure between Macropetalichthys and 

 modern Dipnoans, and this relates to the underside of the head. The 

 parasphenoid was correctly identified as such, and observed to have the 

 usual Dipnoan outline ; but he was less happy in determining the relations of 

 the so called "cerebral chamber" of Newberry, and the structures termed by 

 him " nuchal elements." Cope's " nuchal plate," or " dorsal plate " as it was 

 called by Dean and Eastman, was further misinterpreted by the last named 

 authors in that it was held to represent collectively the dorsal body plates 

 of other Arthrodires, Dean's definition of "Anarthrodira " being based upon 

 this view. Indeed, it must be said frankly that serious misapprehension has 

 existed in the minds of all students, including the present writer, concerning 

 the structures seen within the interior of the head shield in Macropetalich- 

 thys. As in the case of the cranial buckler itself, they only become intelli- 

 gible through comparison with surviving Dipnoans, as will presently be shown. 



