Classification of the Ganoids. 337 



characters will leave them no choice. The Leptolepides and 

 Megaluri have the true biconcave vertebrae of the Teleostei ; 

 but there is nothing astonishing in the fact that there was 

 among the most ancient Teleostei a type (the Caturi) with a 

 more embryonic spinal column — that is to say, with " annular 

 vertebrge" or " semi vertebrae." 



e. If the Acanthodei should be classed with the Ganoids, 

 they will undoubtedly form a separate division ; but I am 

 rather of the opinion of those authors who regard them as a 

 special type among the Chondrostei. The reader will consult 

 with advantage the excellent exposition of this question given 

 by Prof. Huxley in 1861. Lastly, whether we regard this 

 remarkable family as the group of Ganoids most nearly ap- 

 proaching the Selachia, or as the Selachian type nearest to 

 the Ganoids, is not of much consequence in reality. 



f. Finally, with regard to the Placodermi^ I must in the 

 first place declare that I do not understand why so much stress 

 has lately been laid upon the profound diversity of tyj)e be- 

 tween the Ceplialaspides on the one hand, and the Coccostei 

 (with PtericJithys) on the other. Prof. Huxley regards the 

 latter as ti'ue Teleostei, and places the Ceplialaspides provi- 

 sionally with the Sturgeons, at the same time indicating their 

 analogy with the Siluro'idei. In my opinion, these are all ani- 

 mals of uncertain position, " incertce sedis,^^ the true affinities of 

 which still remain to be discovered. If we are still to persist 

 in regarding them as " cuirassed Ganoidsj^ it will be neces- 

 sary to establish for them a special division (fouith or third) 

 in the suborder of Ganoids. 



TVhat^ then J is a Ganoid? If it is absolutely necessary to 

 give a definition, it must be formulated nearly as follows : — 

 Every fish (abdominal, malacopterygian, physostome) icith 

 osseous scales, articulated (as in the Lepidostei) or interlocked 

 (in the manner of the Pycnodonts), or with gular plates injjlace 

 of the hraachiostegal rays, and with the paired fins f-inged and 

 scaly {■a.s. ill ih.& PolyiJteri), or lohich combine several of these 

 characters, loill he classed among the Ganoids *. And with 

 regard to the position and rank which the Ganoids should 

 occupy in the system, it will be necessary to form with them 

 a suborder of the Physostome Teleostei, touching upon the 

 Chondrostei, but separated from these by the Sturgeons, and 

 surrounded by the Jurassic Teleostei, the Amiida3, and the 



* Even if we should prefer to suppress the suborder Ganoidei alto- 

 gether, and to place the three families Lepidosteidce, LcpidopleHridcs, and 

 Polypteridce after the SUuri, Characini, Cjiprini, Salinones, and tlae other 

 physostome families, the term " Ganoid " must still be regarded as a 

 general denomination for these three families, which are so intimately- 

 connected. 



