412 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



the Ganoids. The bony, angular scales which Agassiz 

 had regarded as the chief systematic feature was not in 

 itself sufficiently distinctive, as living Teleostei possess bony 

 scales. Johann Miiller and C. Vogt strengthened the systematic 

 definition of the Ganoids by anatomical features ; Miiller 

 showed that the Ganoids agreed with the Plagiostomes, and 

 differed from the Teleosteans in the structure of their heart. 

 This step in the right direction was not, however, immediately 

 followed by palaeontologists, who on the contrary persist- 

 ently continued to place the Ganoidei in close affinity with the 

 Teleostei. 



A preliminary paper on " Devonian Fishes " was published 

 by Huxley in 1861, and was followed five years later by 

 his memorable work on the Structure of Crossopterygian 

 Ganoids, wherein he showed the relationship of these forms to 

 the Dipnoi. Huxley regarded the genus Lepidosiren as a 

 living representative of the ancient Ganoids; and in 1870 the 

 living genus Ceratodus was discovered, and its careful anatomy 

 and description (1871) by Giinther showed that the new 

 genus was closely allied with Lepidosiren, and that both must 

 be assigned to the Ganoidei. The more accurate knowledge 

 thus secured reacted favourably on the advance of a sound 

 systematic knowledge of the fishes. 



The monograph by Traquair (1877) on The Ganoids of the 

 British Carboniferous Formations made known one of the 

 richest and best preserved Ganoid faunas. The Selachian 

 fishes were made the subject of a comprehensive series of 

 researches by Hasse on the structure and the development of 

 the vertebrae ; O. Jaekel has contributed an excellent mono- 

 graph of the Selachian remains from the Tertiary rocks of 

 Monte Bolca; and O. Reis has written valuable memoirs on 

 Ccelacanthidae, Acanthodidae, and other fossil groups. An 

 admirable catalogue of the fossil fishes in the British Museum 

 is in course of preparation by Smith-Woodward, one of the 

 first authorities on fossil fishes. The volumes already pub- 

 lished (1889-95) present, so far as they go, an exhaustive and 

 critical review of all fossil fishes. 



Amphibians. The works of Alexandre Brongniart (1805) 

 and Blainville emphasised the fundamental differences between 

 Amphibians and Reptiles anatomically, and in respect of the 

 history of their development; but it was Merrem who, in 1820, 



