J. L. Wortman — Cope's Tertiary Vertebrata. 299 



this epoch it would not do very great violence to the system to 

 unite under this order an even greater number of these divis- 

 ions than is done by Professor Cope. The origin of the Car- 

 nivora from the Insectivora through the specialized offshoot 

 Creodonta is demonstrated beyond all peradventure, it seems to 

 us, while many interesting and important facts have been dis- 

 covered which throw a great deal of light upon the philogenetic 

 history of the Dogs and Cats of modern times. 



Although not indicated by Professor Cope, it seems in the 

 highest degree probable that in his Insectivorous genus Esthonyx, 

 we have the ancestor of the Tillodontla, which in turn gave 

 origin to the Toxodoniia. 



Among the Lemuroids many new and interesting genera are 

 added to the list, as well as much important information re- 

 specting them. Prominent among these is the description of 

 the skull of Anaptomorphus, a remarkably specialized form for 

 so early a period as the Wasatch from whose rocks it was 

 derived. Others of scarcely less importance are described and 

 figured. 



Another discovery of importance, which is here recorded, 

 relates to the probable ancestry of certain of the marsupials, 

 including the very curious genera Plagiaulax and Thylacoleo. 

 According to Professor Cope, Ctenacodon of Marsh, from the 

 American Jurassic, is the ancestral type from which these Pia- 

 giaulacid Marsupials were derived. The line of development, 

 as indicated by him, is as follows : Ctenacodon, Plagiaulax, 

 Ptilodus, Calopsolis and Thylacoleo. Ptilodus and Catopsolis, 

 from the Puerco Eocene, are the important links which have 

 been added by Professor Cope, establishing not only an inter- 

 esting fact of phylogeny, but adding at the same time another 

 link to the chain between the Jurassic and Eocene Mammalia. 



Altogether this ponderous volume forms one of the most 

 substantial contributions to the subject which has ever been 

 made, and certainly marks an epoch in the history of paleonto- 

 logical science. The genera and species considered are well 

 systematized and defined, the descriptions clear and accurate, 

 while the illustrations are for the most part well done. That 

 which, however, will in all probability commend the work most 

 to thoughtful students of paleontology, is the unusual grasp of 

 its philosophic deductions which are in every way worthy of 

 the marked ability of its author. 



TJ- S. Army Med. Mus., Washington, D. C. 

 July 16, 1885. 



