RISE OF MODERN FISHES 



171 



a whole fossil series of these archaic fish types as they lived 

 together in the fresh water or the brackish pools of Upper De- 

 vonian time. (Fig. 51). 



In this period the palaeogeographers (Schuchert) obtain their 

 first knowledge of the evolution of the terrestrial environment 

 in the indications of the existence of parallel mountain ranges 

 on the British Isles, of active volcanoes in the Gaspe region of 



PALEOOEOGHAPHY. EARLY LOWER DEVONIAN (HELDERBERGIAN-GEOINNlAN-HEHOYNfAN-KONIEPRUSSIAN) TIME 



AFTER SCHUCHEnr. APRIL. 1916 



^ ^^MARINE DEPOSITS ^-^CONnNENTAL DEPOSITS ^' MOUNTAINS AND VOLCANOES 



Fig. 52. Theoretic World Environment in Early Lower Devonian Times. 



The period of the early appearance of terrestrial invertebrates and vertebrates. This 

 shows the hypothetical South Atlantic continent Gondivana and the Eurasiatic inland 

 sea Tethys, according to the hypotheses of Suess. Modified after Schuchert, 1916. 



New Brunswick, of the mountain formations of South Africa, 

 and of the depressions of the centre of the Eurasiatic continent 

 into the great central Mediterranean Sea, known as the Tethys 

 of the great Austrian geologist, Suess. In the seas of this time, 

 as compared with Cambrian seas, we observe that the trilo- 

 bites are in a degenerate phase, the brachiopods are relatively 

 less numerous, the echinoderms are represented by the bottom- 



