SYNCHRONISM OF GEOLOGICAL FORMATIONS. 233 



the association in the Gondwana system of a Jurassic flora with a 

 Triassic fauna, or of a Tertiary flora and Cretaceous fauna in the 

 Laramie deposits of the United States. Less intelligible is the 

 reported superposition in the Gondwana rocks of a Rhaetic flora 

 upon one of a Jurassic facies, and of a Triassic or Permian fauna 

 upon one of Jurassic age. As far as the faunal evidence is con- 

 cerned, both as relates to the "Triassic" or "Permian" and the 

 " Jurassic " types, it is so slender as to permit no safe conclusion 

 being based upon it. Thus, the only animals thus far recorded 

 from the Damuda (Jurassic) beds are an Estheria and two laby- 

 rinthodonts, one of which, Brachyops, is claimed to be allied to a 

 European genus from the Oolites. Equally imsatisfactory is the 

 Permian relationship that has been attached to the vertebrate fauna 

 of the overlying Panchct beds, which comprises three genera (four 

 species) of labyrinthodonts, whose nearest allies are found in the 

 European Trias, one species of dinosaur, and two dicynodonts, 

 believed to be nearly allied to forms described from what are now 

 recognised to be Permian rocks of the Ural Mountains. The very 

 limited number of species found in these deposits, together with 

 tlieir uncertain relationship, is scarcely sufficient to identify a fauna, 

 and it must, therefore, be concluded that we are still far from 

 having evidence of a positive character proving an inversion in the 

 faunal series, or as indicating any important difference between 

 homotoxis and synchrony, where marine fossils are taken as the 

 determining guide.* The advantages possessed by these last over 

 others of a terrestrial nature for the purposes of geological classifi- 

 cation are obvious from their broad distribution and equal chrono- 

 logical development. 



* Mr. Lydekker, discussing the remarkable labyrinthodont Gondwano- 

 saurus from the Bijori group, maintains that the balance of evidence is ia 

 favour of regarding the Panchct beds as of Triassic age ; the age of the Damuda 

 beds is left in doubt (Palaeontologia Indica, 1885). 



