PHYLOGENY. 89 



the subclass Stegocephali in the overroofing of the 

 posterior regions of the skull ; in the presence of vo- 

 merine teeth, and in the absence of obturator foramen 

 of the pelvis. In some Cotylosauria (Diadectidae) the 

 stegocephalian tabular bone of the skull is well devel- 

 oped. But in the Cotylosauria, the vertebral column 

 consists mainly of centra, while in the Stegocephali it 

 consists entirely or partly of intercentra. But in the 

 Embolomeri the centra are well developed, and are 

 larger than the intercentra anterior to the pelvis. 

 Hence this is the only order of Stegocephali from 

 which the Reptilia could have been derived. 



Haeckel derived the Batrachia from the Dipnoi 

 (Dipneusta), and I followed him in this belief, being 

 strengthened in it by Huxley's ascription of an auto- 

 stylic suspensorium of the mandible 1 to both divisions. 

 This phylogeny is questioned by Pollard 2 and by Kings- 

 ley, 3 who would see the ancestry of the Batrachia in 

 the crossopterygian fishes on embryological grounds 

 derived from a study of Polypterus. In support of 

 their view I would cite the absence of the maxillary 

 arch in the Dipnoi, and its full development in the 

 Stegocephali, which are the ancestral Batrachia. The 

 large development of the dorsal and anal fins in the 

 Dipnoi is not favorable to the Haeckelian view; nor 

 do the paired fins approach as nearly to the limbs of 

 Batrachia as do those of some other fishes. It has been 

 shown by Huxley that the suspensorium of the Ba- 

 trachia is hyostylic in its earliest stages, and that it 

 becomes autostylic at a later period of development. 



1 Proceedings Zoological Society of London, 1876, p. 59. 

 1 Anatomischer Anzeiger, VI, p. 338, 1891. 



3 American Naturalist, 1892, p. 679. Kingsley would also derive the Dip- 

 noi from Crossopterygia. 



