XI 



The author, after a careful review of the subject, is compelled to agree 

 with Messrs. Kner, Owen, Liitken, and Cope in the closer combination of 

 the Teleosts, Ganoids, and Dipnoans and the contradistinction of the 

 united group from the Elasmobranchiates, and is even disposed to admit 

 that the range of variation in the Ganoid series is so great that less differ- 

 ence appears to exist between the most teleosteoid Ganoids (e. g., Amid) 

 and the Teleosteans than between them and the most generalized Ganoids 

 (e.g., Polypterus and Acvpenser). But, notwithstanding this, the estab- 

 lishment by Johannes Miiller of the subclass for which he adopted the 

 name Ganoidei appears to have been one of the most important in the 

 histoi'y of Ichthyology, as it was the expression of the discovery of char- 

 acters which undoubtedly indicate affinity, and, however much recent 

 Ichthyologists hd,ve dissented from him as to the boundaries of groups, all 

 have left the Ganoids in immediate juxtaposition to each other, and have 

 chiefly differed from him as to the point where the primary division should 

 be established, whether on one side or other of the Miillerian Ganoids. 



In the following list of families, the three subclasses of true fishes estab- 

 lished by Miiller are still retained, but are combined under two series, 

 Teleostomi (Owen) and Elasmobranchii (Bon., Mull.), and the several 

 superorders are distinguished among the Ganoids. For while the author 

 is prepared to admit that the extremes of the Ganoids are more dissimilar 

 than one of those extremes and the typical physostome Teleosts, it is not 

 yet apparent that the relations between the Ganoids and Teleosts are as 

 intimate as those between the contiguous orders of the latter series. 



ORDERS OF PISCES. 



After a recent review of the various proposals for the modification of 

 the system by various authors, and due examination of the animals them- 

 selves, the author is compelled to retain the orders of Teleosts adopted in 

 the classification proposed by him in 1861, suppressing, however, the (then 



Description of Ceratodus, a genus of Ganoid Fishes, recently discovered in 



rivers of Queensland, Australia. .... < Philosophical Transactions of tho 

 Royal Society of London, v. 161, 1872, pp. 511-571, pi. 30-42. 

 Dr. Giinther recognizes only two orders among Palaeichthyes, viz : — 

 Fourth subclass : Pal;eichtuyes. 

 Order 1. Chondropterygii. 

 Suborder 1. Plagiostoma. 

 Suborder 2. Holocephala. 

 Order 2. Ganoidei. 

 Suborder 1. Arnioidei. 

 Suborder 2. Lepidosteoidei. 

 Suborder 3. Tolypteroidei. 

 Suborder 4. Chondrostei. 

 Suborder 5. Dipnoi. 



