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GANOID FISHES OF THE CARBONIFEROUS FORMATION. 



Sub-order — Lepidosteidei, Huxley. 



Family I. Lepidosteini, Huxley {Lepidosteus). 

 II. Lepidotini, Huxley. 



f Homocercal Forms. 



Sub-family 1. Sauroidei (Ag.), A. Wagner {Pholidophorus, PJugnathus, &c). 



2. Stylodontes, A. Wagner {Tetragonolepis, Dapedius, &c.). 



3. Splicer odontes, A. Wagner [Lepidotus, Plesiodus, &c.). 



4. Aspidorhynchi, A. Wagner (Aspidor/iync/ius, Belonostomus, &c.). 



t t Heterocercal Forms. 

 Sub-family 5. Palaoniscini, Vogt {Amblypterus, Palceoniscus, &c.). 



Family III. C/ieirolepidini, Pander {Cheirolepis) . 



It must at once strike the zoologist who is at all practically acquainted with the 

 structure of these fossil forms, that the association of the Palgeoniscoid Fishes in one 

 " family " with such genera as Lepidotus, Eugnathm, and Aspidorynchus is rather at 

 variance with the usually received ideas of the limits of " family " comprehensiveness in 

 other divisions of the class Pisces, or of the animal kingdom in general. Not only so, 

 but Cheirolepis, whose resemblances to other Palceoniscidce are perfectly plain and 

 obvious, remains as the type of a distinct family, equivalent to the whole assemblage of 

 " Lepidotini," in which its natural allies are placed as a mere " sub-family/' The 

 affinities of the Liassic Palaoniscidce are still unrecognised, Oxyg?iathus, Cosmolepis, 

 T/irissonotus, and Centrolepis being placed in the sub-family " Sauroidei," while the 

 imperfectly heterocercal genus Catopterus is associated with Palceoniscus. 



From the preceding sketch of the history of the classification of the Palceoniscidce it is 

 pretty clear that at present the generally received opinion is that the Palseoniscoid Fishes 

 belong to the Lepidosteoid series or sub-order. We may now inquire how far that conclu- 

 sion is in accordance with the details of their structure brought out in the preceding part 

 of this essay. 



First, however, it is necessary to lay down with some degree of conciseness the 

 leading characters, however few, of that series of fishes to which we give the name of 

 Lepidosteidce, or, as I think is preferable, Lepidosteoidei. Now, though Lepidosteus 

 itself is rather aberrant in the form of its vertebral centre, and of its prseoperculum, in the 

 composite character of its maxilla, and in the small number of its non-enamelled bran- 

 chiostegal rays, yet its relationship to a large series of fossil forms is, as regards more 

 general characters, sufficiently evident to justify our placing them together in one category, 

 though the complete working-out of the group is one of several tasks which fossil 



