HUXLEY AND HIS WORK. 771 



Finally, in 1876, Huxley published, as "No. 1" of "Contributions to 

 Morphology," a memoir "On Geratodus forsteri, with observations on 

 the classification of fishes." He still persisted in separating the recent 

 Dipnoans from the extinct forms combined with the Crossopterygidse, 

 and contended that "even Dipterus, which approaches Geratodus and 

 Lepidosiren so closely in its dentition and in the form of its fins, is far 

 more similar to Polypterus and Amia in other respects; and there is at 

 present no reason to believe that any of the Crossopterygian Ganoids 

 possessed other than a hyostylic skull, or differed from Polypterus in 

 those respects in which Polypterus differs from the existing Dipnoi. All 

 known Crossopterygians have jugular plates, of which there is no trace 

 in the Dipnoi." 



It will be thus seen that the suborder of Crossopterygidas was really 

 the result of a misunderstanding and included most Dipnoans (and to 

 such extent was a synonym for that group) as well as the Crossopteryg- 

 ians of later authors. It was by no means the exact equivalent of 

 Crossopterygians, and consequently the latter name can not be consid- 

 ered as a synonym of Crossopterygidaa or be replaced by it. Neverthe- 

 less the introduction of the so-called suborder was not only the expres- 

 sion of an advance in our knowledge of the system itself, but paved 

 the way for future investigators. 



I am even inclined to credit mainly to his sagacity the early appreci- 

 ation of the affinity of the Neoceratodus of Australia to the mesozoic 

 Ceratodontids with all the far-reaching consequences that appreciation 

 involved. It was in 1870 that the living Ceratodontid was introduced 

 to the scientific world as Geratodus forsteri, and thus generically associ- 

 ated with the mesozoic fishes. How did Krefft (or Clarke) get the idea 

 of this association of a living fish with some known only from fossil 

 teeth referred by Agassiz to the same family, as the Cestraciont sharks? 

 In 1861 Huxley published his Preliminary Essay upon the Systematic 

 Arrangement of the Fishes of the Devonian Epoch, and therein sug- 

 gested that Geratodus was a Cteuodipterine fish and ranged it (with a 

 mark of interrogation) by the side of Dipterus. He also drew "attention 

 to the many and singular relations which obtain between that wonder- 

 ful and apparently isolated fish, Lepidosiren" and the Cteuodipterine 



Dipnoi and Polypteroids, and for that reason combined the two in the subclass 

 Ganoidei. In a discussion of the subject (Cat. Fishes N. Am., p. 15;, I remarked 

 that "Milne-Edwards again urges as a previously neglected argument in favor of 

 the amphibian nature of Lepidosiren, the opening of the ductus pneumaticus of the 

 pulmonary sacs into the ventral face of the digestive canal. But we also find a 

 similar arrangement in the species of the genus Polypterus, animals whose piscine 

 character and affinities have never been called in question;" also, "It is a fact of 

 no little interest that the Polypteri, which have an air bladder so similar to that of 

 the Lepidosirenes, do also, of all known fishes, most resemble them in the form and 

 development of the different elements of the brain." They differ, however, in car- 

 diac and osteologic characters. I concluded that "as the Dipnoi agree in all other 

 essential respects with the Ganoids, we will then at least provisionally consider 

 them as belonging to the same great subclass." 



