Prof. E. D. Cope on the Sf/stematic Relations of Fishes. 161 



tlie case -vvitli any other two of tlie classes adopted above. The 

 peculiarities of the limbs, important as they are, are nearly 

 related in the Avant of specialization of their parts, seen in the 

 Batrachia and other classes — the difierences consisting rather 

 of number and position of similar parts. The pelvis of the 

 Dipnoi might be regarded as of primary importance but for 

 its existence in the Holocephali, whose limbs, again, are so near 

 those of the shark. 



It remains, therefore, to adopt the Linna^an and Cuvierian 

 class Pisces, and to grant as subclasses the groups of Holo- 

 cephali, Selachii, and Dipnoi. There remain as subclasses 

 the groups typified by Polyj)te7-us on the one hand and the true 

 fishes on the other. The first has been already distinguished 

 in its external characters by Professor Huxley, who again 

 brought light out of obscurity when he established his " third 

 suborder of Ganoids, the Crossopterygidge, " This division is, 

 in my estimation, a natural one, and to be elevated to a rank 

 equivalent to that of each of the three above named, being the 

 only part of the original division of Ganoids of Miiller entitled 

 to it. Professor Huxley .defined it as follows : — 



" Dorsal fins two, or, if single, multiplied or very long ; the 

 pectoral and usually the vertical fins lobate ; no branchiostegal 

 rays, but two principal, with sometimes lateral and median ju- 

 gular plates situated between the rami of the mandible ; caudal 

 fin diphyocercal or heterocercal ; scales cycloid or rhomboid, 

 smooth or sculptured." 



Of the above characters, that which relates to the lobate fins 

 is the essential one, and is the expression of the external ap- 

 pearance produced by the structure of the bones of the limbs 

 already pointed out by Gegenbaur. The dorsal fins of some 

 families, it is true, possess a remarkable structure; but in Pha- 

 neropleuTon (Huxley) and some others they appear to be nearly 

 like those of the Dipnoi. The absence of branchiostegal rays 

 is important, but is shared by the Sturgeons. The jugular 

 plates appear to exist in Polypterus alone among recent fishes, 

 though several, as Amia, EloiJSj Osteoglossum, &c., possess a 

 median one. Nevertheless its nature would not lead one to 

 anticipate its being a constant feature in any group of high 

 rank ; at least such is our usual experience Avith dermal bones. 

 The structures of the skin and scales given by Huxley are 

 very subordinate. 



The remaining division answers, then, to the Teleostei and 

 Ganoidei of Miiller, minus Pohjjyterus. The name Teleostei 

 cannot be preserved for this division, owing to its entire want 

 of coincidence with that division of Miiller, as well as from the 

 fact that the cartilaginous Sturgeons must be included in it. 



