EDWARD D. COPE. 61 



Omitting from consideration the two classes above 

 mentioned, whose remains have not yet been certainly 

 found in a fossil state, there remain the following : the 

 Pisces, Batrachia, Reptilia, Aves and Mammalia. 



The Mammalia have been traced to the theromorphons 

 reptiles by the Monotremata, The birds, some of them 

 at least, appear to have been derived from the Dinosau- 

 rian reptiles. The reptiles in their primary representa- 

 tive order, the Theromorpha, have been probably derived 

 from the embolomerous Batrachia. The Batrachia have 

 originated from the subclass of fishes, the Dipnoi, though 

 not from any known form. I have shown that the true 

 fishes or Teleostomi have descended from an order of 

 sharks, 1 the Ichthyotomi, wiiich possess characters of 

 the Dipnoi also. The origin of the sharks remains en- 

 tirely obscure, as does also that of the Pisces as a whole. 

 Dohrn believes the Marsipobranchii to have acquired its 

 present characters by a process of degeneration. The 

 origin of the Yertebrata is as yet entirely unknown, 

 Kowalevsky deriving them from the Ascidians, and 

 Semper from the Annelida. 



The above results I have embodied in the following 

 phylogenetic diagram : 



Aves Mammalia 



r Teleostomi 



! 



Pisces -J Selachii Ichthyotomi 

 1 ^\ 1 ^ 



Reptilia 



/ 



Batrachia 



\ 



Dipnoi 



Holocephali 



IVTl TCI V\/~*l^l 



Leptocardii 



lYlcli oi jJU U\ 



1 Proceedings Am. Phi). Soc., 1884, p. 585. 



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