BY MRS MILLER. xIt. 



}!ugh Miller in the " Eoot-prints" and his other works. 

 But this Owen divides into two sub-orders, viz., placo-ga- 

 noids, or ganoids covered with plates ; and lepido-ganoids, 

 or those covered with scales. In the former he places the Ce- 

 phalaspidse, including PteraspisLudensis, — the earliest known 

 fish, — Coccosteus, Pterichthys, Asterolepis, &c. The lepido- 

 ganoids include the Acanthodes, Diplacanthus, Cheiracan- 

 thus, and Cheirolepis ; likewise the Coelacanths, as Glypto- 

 lepis, Phyllolepis, and the Holoptychidae. 



Professor Huxley, on the other hand, demurs altogether 

 to Agassiz's ganoid order, as it at present stands. He ex- 

 cludes from it the Siluroids (the analogues of the Cephalaspi- 

 dse), asserting that they are in no respect different from Tele- 

 ostei or true bony fishes, and says that the true ganoids are in- 

 termediate between the Teleostei and Elasmohranchii, or what 

 are commonly called cartilaginous fishes. In this he follows 

 Johannes Miiller, " since whose researches," he says, " the 

 term Ganoidei has been received in a very different sense by 

 the great mass of naturalists." The term is restricted by 

 Huxley to six genera of existing fishes ; but as the charac- 

 teristics depend on certain peculiarities of the brain, of the 

 optic nerve, the aorta, &c., they must for ever remain undis- 

 cemible by the great mass of readers, to whom Agassiz's 

 classification has the great advantage of being simple and 

 easy of comprehension. Indeed, whether any classification is 

 possible which, in the nice gradation of nature's handiworks, 

 shading off in all directions, does not include some anomalies, 

 remains to be seen. With regard to these differences of 

 opinion, Sir Philip Egerton writes me (with a kind permis- 

 sion to quote from his letter) as ^-^ows : — " I am of opinion 



