OCT. 1895. VERTEBRAL COLUMN OF AMIA HAY 23 



By the consent of perhaps all modern ichthyologists, the relation- 

 ships of the Ganoids and the Teleosts are very close. Dr. Gill (31) 

 regards the two groups as distinct subclasses, but admits that in some 

 of their members they approach closely. Liitken (46) excludes from 

 the Ganoids large groups which have been held to belong there. 

 Among these excluded forms are the Amioidei. Others abandon the 

 conception of the Ganoids as forming a distinct group. Cope forms 

 of the bony fishes, and some of the Ganoids, his subclass Actinopteri. 

 It is hardly open to doubt that the Teleosts have descended from more 

 or fewer of the families of ancient Ganoids. The Halecomorphi are 

 intimately related to the Isospondyli, and have probably furnished 

 the ancestors of the latter. Hence we might reasonably expect to 

 find in some of the recent or fossil Teleosts, in the stricter sense, 

 traces of the composite nature of the vertebral centra. And in fact 

 Prof. Cope (22) expresses the opinion that the fossil genera which 

 possess annular vertebrae, as Aspidorhynchus, should be assigned to 

 Isospondyli. According to the views of Liitken, most of the genera 

 which display pleuro-and hypocentra would be thrown among the 

 Teleosts. The Hoplopleuridae, whose members range through the 

 Mesozoic, are now usually assigned to the Teleost series. In some of 

 these the vertebral column is imperfectly or not at all ossified. Be- 

 lonorhynchus has feebly ossified vertebrae. The vertebral elements 

 appear as small ossifications at the bases of the arches, and are prob- 

 ably to be regarded as pleuro-and hypocentra. Deecke (24, p. 131) 

 points out the close resemblance of this fish to Be/one belone, living 

 now in the Atlantic. He states that if the vertebral column-of Bel- 

 onorhynchus were ossified it would be difficult to distinguish the two 

 genera. We are therefore justified in expecting that our living 

 Teleosts will in some way display in their vertebral structure the 

 existence of the elements which we have found in so many of the 

 Ganoids. Nevertheless, we are not yet in a condition to demonstrate 

 the presence of such elements. The vertebrae of our fishes have not 

 yet been investigated sufficiently from this point of view to enable 

 us to speak with definiteness. 



It is, of course, entirely possible that in the lapse of ages one or 

 the other of the elements of the vertebral centrum of the ancient 

 fishes has entirely disappeared, while the other remains as its sole 

 constituent. And this is what Prof. Cope appears to believe has hap- 

 pened. He says (22, 1019) : " The so-called centra of fishes are inter- 

 centra [hypocentra], as in the Batrachia." This opinion may be cor- 

 rect, but the grounds on which it appears to have been based seem to 

 afford it insufficient support. " The descriptions and figures of Prof. 



