ON THE GENUS CTENODUS. 101 



he classified it among the Fishes as a Plaeoid ; but, beyond naming 

 the genus and species, he did little more ; what remarks he 

 makes will be found in his " Poissons Eossiles" tome iii. The 

 species he founded were C. alatus and C. asteriscus from the 

 Devonian formation, and C. cristatus, C. Murcliisoni, G. Mohert- 

 soni, from the Carboniferous. Professor Owen falls into the same 

 error with regard to. the classification of this fish. That Agassiz 

 and Owen should have erred in thus classifying Ctenodus is not 

 to be wondered at, for they were only acquainted with the dental 

 plates, and had no other fish presenting teeth of this type to refer 

 to ; any ichthyologist having only the teeth before him would 

 make the same mistake, for they are unmistakeably Cestraciont 

 in character. Hugh Miller, while examining Dipterus, another 

 Devonian fish, discovered that it possessed teeth similar to those 

 of Ctenodus; this discovery tended to show that Agassiz and 

 Owen were mistaken in considering Ctenodus to be a Plaeoid, as 

 Di-pterus is, without doubt, either a member of the Ganoidei or 

 the Dipnoi \ the majority of palaeontologists at present placing it 

 as a Ganoid. Other fish remains were obtained, and named 

 Geratodus and Tristy diopter us, with similar teeth. These four 

 fossil genera, Dipterus, TristycTiopterus, Geratodus, and Ctenodus, 

 were arranged by Professor Huxley, in his synopsis of the 

 Oanoidei, in a family, which was named, Ctenododipterini by 

 Professor Pander, having the following characters : — Two dorsal 

 fins placed far back ; acutely lobate pectoral and ventral fins ; no 

 branchiostegal rays ; jugular plates ; single anal fin ; caudal 

 extremity tapering to a point ; lower lobe of tail much larger 

 than upper ; scales cycloidal and smooth ; bones of cranium 

 anchylosed into a shield ; lower law of peculiar form ; dentition 

 ctenodont. Eichwald, in the first volume of his " Lethsea 

 Eossica" further adds that Gtenodipterines have solid and distinct 

 bodies in their vertebrae, and that their scales are rounded and 

 imbricated besides being cycloidal. Dr. A. Giinther, in his 

 paper to which I have already referred, seems clearly to prove 

 that Geratodus belongs to the Dipnoi ; if this be so, then Ctenodus 

 must also do so, for these two fishes in their internal skeleton are 

 similar in every respect so far as we know as yet ; the complete 

 tail of Ctenodus has not been discovered up to the present time, 

 it may possibly differ from that of Geratodus, but seeing that the 

 fishes agree so far as their bony remains are concerned, it is not 

 probable. However, while there is this uncertainty we will not 

 dogmatize upon the matter, but will leave it an open question to be 

 decided by future discoveries ; still, it may safely be predicated that 

 Ctenodus is related to whatever family Geratodus may belong. From 

 a private letter that I received in May last I learn that Professor 

 Huxley has been lecturing during the past winter upon the relation- 

 ship between Geratodus and Dipterus, but, strange to say, he never 

 spoke of Ctenodus, which is even more closely allied to Geratodus. 



