1897.] Palwontology. 977 
same paper he designated, Cope’s intercentrum as “ Pièce inférieure du 
centrum.” I do not believe that there has been any uncertainity 
about the morphology of the vertebral column of the Stegocephali and 
the higher Vertebrates. The whole question was definitely solved. 
Everybody is convinced that the pleurocentra of the Rachitomi re- 
present the centra of the higher Vertebrates; and that the intercentra 
are homologous to the intercentra of the Sphenodontide, Geckonide, 
Uroplatidx, Pelycosauria. These intercentra support in the tail the 
chevron bones, or hæmal arches; both are firmly united. 
In some papers published this year by Dr. Hans Gadow’ and Prof. 
Alexander Gotte,? it is maintained, that the intercentrum of the 
Rachitomi forms the centrum of the Amniota; Prof. Jackel comes to 
the same conclusion. Gadow and Gétte have never examined any 
fossil Stegocephali or Pelycosauria and Jiickel, by some unfortunate 
caleulation, has completely misunderstood the true nature of the 
archegosaurian vertebral column. 
I shall show that this new opinion is in opposition to all morpholog- 
ical facts. In Archegosaurus the rib-heads are articulated below with 
the intercentrum, behind with the pleurocentrum and above with the 
pointed base of the neural arch. In the tail the lower arches (hemapo- 
physes, chevron bones) are united with the intercentra. In the Pely- 
cosauria; Clepsydrops, Dimetrodon, Naosaurus, Embolophorus, Thero- 
pleura and others we have exactly the same condition. There are very 
well developed intercentra between the centra, which are suturally united 
with the neural arches. The capitulum the lower part of the rib-head 
is articulated to the intercentrum, the tuberculum to the anterior por- 
tion of the centrum and the base of the upper arch. In the tail the 
lower arches (hreemapophyses, chevron bones) are united with the inter- 
centrā, 
According to Gadow, Götte, Jäckel the Intercentrum Cope, of the 
Rachitomi is homologous to the centrum of the Amniotia. There is no 
doubt, that the intercentrum plus hemal arch (chevron) of the Pelyco- 
sauria is homologous to the intercentrum plus hemal arch (chevron), of 
Archegosaurus; therefore the intercentra of the Pelycosauria are 
centra, according to the authors named above. Therefore, the Pelyco- 
sauria have two centra. This of course is absurd, therefore the 
™Gadow, Hans. On the evolution ofthe vertebral column of Amphibia and 
Amniota, Philos. arai Roy. Soc. London, vol. 187 (1896), B. pp. 1-57. 
pipe 1896, June 1 
lex. Seber den Wirbelbau bei den Reptilien ond einigen anderen 
Wee Zeitschr, wissensch. Zool., vol. LX V, p. 843-394. 
