﻿212 Miss Agnes Crane — On Certain Living and Fossil Fishes. 



the elements of the internal skeleton, and above all the co-existence 

 of a lung with gills, show how close is the affinity between the 

 Australian Ceratodus and the mud-fishes of Africa and South 

 America, and although the former approach less to the amphibian 

 type than the latter, it is obvious that in a natural classification their 

 place is side by side. 



Fossil Affinities of the Dipnoi. — Having shown the close 

 connexion between the two genera of living dipnoids, let us 

 now consider the relations of the living and fossil Ceratodonts. 

 No remains of this genus have as yet been found in the Tertiary 

 or Cretaceous formations ; but the fossil teeth, of which several 

 varieties are recognizable, possibly the relics of numerous species, 

 occur abundantly in the Triassic beds of Aust Cliif, near Bristol, 

 and in the Muschelkalk of Germany. They have also been ob- 

 tained from strata now determined to be of Triassic age at 

 Maledi, south of Nagpur, in India, and associated, as in Europe, 

 with the reptilian remains Hyperodapedon. Many of these fossil 

 teeth are much larger than those of the existing species (specimens 

 of one Triassic form measure over two inches in length), and must 

 necessarily have belonged to individuals of a gigantic race. The 

 dental plates only have been found fossil, but the structure of 

 Ceratodus Fosteri indicates that they alone of a like-constructed 

 animal would be susceptible of preservation in sedimentary strata, 

 and the classification of the recent forms with those of the Mesozoic 

 rocks, separated by so wide a gulf of geological time, though 

 founded on the similarity of the dentition alone, is the only reason- 

 able one, as there is no evidence that the living and fossil Cerato- 

 donts, differed from each othei'. The teeth of this genus resemble 

 in general shape and structure those of Ctenodus which are widely 

 distributed in Carboniferous strata, species occurring in America 

 being identical with those of the British rocks of contemporaneous 

 age. Tlie dentition of the Devonian Bipterus is also closely related 

 to that of Ceratodus, as well as Lepidosiren} 



Thus the history of the Dipnoi, an oi'der before the discovery of 

 the Australian Ceratodus only represented by the mud-fishes of Africa 

 and South America, is carried back to remote geological ages, and 

 the four living repi'esentatives, at present known, are found to be 

 the survivors of a well-defined and characteristic group of fishes first 

 appearing in the Devonian age. They can be traced up from Dip- 

 terus, through the Carboniferous Ctenodus, to the Jurassic Cerato- 



1 Prof. J. S. Newberry (vol. ii. Palasontology of Ohio, p. 63, pi. 58, fig. 18) 

 recognizes in his new genus Heliodus, occurring in the Upper Chemung group of the 

 American Devonian, the most gigantic member of the family of dipterine ganoids to 

 which Ceratodus, Ctenodtis, and Bipterus belong. The teeth resemble in microscopic 

 structure those of Bipterw, and in general shape those of Ctenodus. The upper 

 palatal ones differ, however, from those of all other known dipnoids in being united 

 "in the form of a fully-opened fan." He is also of opinion that the Falmdaphm 

 insignis of Van Beneden and de Koninck, from the Carboniferous strata of Belgium, 

 is not generically identical with the P. Devoniei/sis, of the same authors, and while 

 admitting that the former is really a Plagiostome, considers that the latter should 

 be associated with his new dipterine genus under the designation of Heliodus 

 Devoniensis. 



