Dr. R. H. Traquair on the Genus Dipterus. ;3 



to the conclusion that Dipterus has a better right to be asso- 

 ciated with the living Dipnoi than with Polyjjterus'''' *. 



Prof, Huxley, however, in his recent and very valuable 

 paper on Ceratodus, takes a different view of the matter f. 

 In this paper Prof. Huxley performs the great service to 

 science of pointing out that in their " autostylic " skull the 

 Dipnoi differ essentudly from the Ganoidei, which are " hyo- 

 stylic ; " and in reference to Dr. Giinther's proposed classifica- 

 tion he concludes " that it is better to retain the Miillerian 

 groups of Dipnoi (Sirenoidei, Miiller), Ganoidei, Teleostei, 

 Plagiostomi, and Chimasroidei (Holoce])hali, Miiller) as equi- 

 valent and distinct natural assemblages." And as regards 

 Dipterus^ he seems to consider that its place is with the 

 Ganoids, saying concerning it, " But even Dipterus^ which 

 approaches Ceratodus and Lepidosiren so closely in its denti- 

 tion and in the form of its fins, is far more similar to Poly- 

 jpterus and Anna 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 Poly- 

 pterus 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. And as to 

 the position of the anterior nares, which appear to have been 

 situated on the under face of the broad snout, not only in 

 Dipterus^ but in Osteolepis and Dipilopterus, I have shown 

 above that, so far from being a diagnostic character of the 

 Dipnoi, it is simply an embryonic feature retained in them, 

 the Selachians, and very probably in many of the earlier 

 Ganoidei." 



In a recently published memoir on Ceratodus \j Mr. L. C. 

 Miall follows Dr. Giinther in classifying Ceratodus and Lepi- 

 dosiren with the Ganoidei ; and as regards the special affinities 

 of the Ctenododipterini, the following statements made by him 

 may be quoted : — 



" We do not know for certain that Dipterus and Ctenodus 

 are hyostylic ; but the suggestion has a certain degree of pro- 

 bability." But in a footnote appended to this passage he 

 states, " The fossil suspensorium of Dipterus, marked xvif , in 

 the Museum of Practical Geology seems to show that this 

 genus agrees with Geratodxis rather than with Polypterus in 

 the mode of suspension of the mandible ; but a fuller discus- 



* " Description of Ceratodus;' Phil. Trans. 1871. 



t Proc. Zool. Soc. London, 187G, p. 57, 



X "On tlie Genus Ceratodus^ with special reference to the fossil teeth 

 found at Maledi, Central India," Pakeont. Ind. ser. iv. 2, Calcutta, 

 1878. See also the same writer's memoir on the " Sirenoid and Cros- 

 sopteiygian Ganoids," Palceoutograph. Society, Lond. 1878. 



1* 



