Classification of the Ganoids. 331 



ance with their affinities and the totality of their characters, 

 species by species and genus by genus, until tlie families are 

 formed ; and then, by bringing together the families in the 

 same manner, without any preconceived idea, we shall succeed 

 by degrees in establishing groups of a higher order, and finally 

 see rise before us the true natural system, the subdivisions of 

 which will rest upon the solid basis of experience and the 

 totality of the facts. We must therefore, provisionally at least, 

 limit the name of Ganoids to the indubitable existing types 

 (that is to say, the Lepidostei and Polypteri) , and to the fossil 

 types which will naturally group themselves around these, by 

 giving proofs of their affinity rendered incontestable by the 

 absolute concordance of important cliaracters ; whilst we must 

 in the same way eliminate, at least provisionally, all the forms 

 between which and the preceding our comparative synthetic 

 method shall prove incapable of establishing any bond of 

 relationship. The picture which the suborder Ganoidei will 

 present to us after a scrupulous investigation of this kind will 

 be nearly as follows : — 



I. First series. — The Lepidosteidce or Eugano'idei will in- 

 clude the fishes with bony, enamelled, rhomboidal, and articu- 

 lated scales, related to the existing Lepidostei^ and possessing 

 neither the dermal ribs of the Lepndojyleimdoi^ nor the fringed 

 or oar-like paired fins of the Polypterida^^ nor the gular plates 

 which take the place of the brauchiostegal rays in the latter*. 

 Although apparently forming a very natural group, there is no 

 positive peculiarity which characterizes these in an absolute and 

 exclusive manner. As regards the scales of the body, they 

 possess characters common to a portion of the Polyptteridce ; 

 the so-called fuJcral scales of the margins of the fins, which 

 occur at least in the majority of the fossil Lepidosteidce ^ occur 

 also in the ancient Lepidopleuridce., and even in some true Te- 

 leostei of the Jurassic period ; leaving out of consideration the 

 living Lepidostei^ the fossil Lepidosteidoi appear to have had a 

 common character in the delicate and numerous rays of the 

 fins and brauchiostegal membrane ; lastly, the forward position 

 of the ventral fins upon the middle of the belly will also dis- 

 tinguish them from the Polypiteridce with similar scales. 



Although this series embraces a very great number of 

 genera, the greater part of which will be found mentioned in 

 my memoir, it seems to me to be impossible to subdivide it 

 naturally into tribes or families. We might perhaps distin- 



* With the sole exception of CJieirolepis, the ouly Devonian tj'pe of the 

 whole series which indicates by its gular plates a certain relationship to 

 the contemporaneous Polypteridfe. 



