CHAPTER XII 



THE TRIASSIC SYSTEM 



WITH the close of the Permian period the last remnants of 

 Palaeozoic life became extinct in the British area, and when after 

 a long continental period the western and northern parts of Europe 

 were again submerged beneath the sea, the waters were tenanted by 

 a very different set of generic forms. The Palaeozoic Groups of 

 Cystid and Blastoid Echinoderms, Rugose Corals, Eurypterids, 

 Trilobites, Goniatites, and most of the Palaeozoic genera of Nauti- 

 loidea had died out, their place being taken by the Euechinoids, 

 Aporose Corals, Siphonate Gastropods, and Cephalopods of the 

 Ammonite and Belemnite type ; many orders of Eeptiles appear 

 for the first time, and the earliest Mammal yet known occurs in 

 the upper beds of the Trias. 



The fish of the Triassic and Jurassic periods also exhibit 

 remarkable changes and developments. The Rhizodont Crossop- 

 terygian fishes of the Devonian and Carboniferous, and the hetero- 

 cercal Palaeoniscids of Carboniferous and Permian time now become 

 scarce ; while a new type of fish (the Protospondyli) with a nearly 

 homocercal tail and a more bony endoskeleton having a tendency 

 to form vertebrae, make their appearance and lead up to the com- 

 pletely vertebrate Teleosteans. 



Even where a continuous series of marine deposits bridges over 

 the gap in the history of marine life which exists in Northern 

 Europe we find that the above remarks are still practically true, 

 the only exception being the existence of a few Gastropod genera 

 and a few species of Orthoceras in the Trias of the Alps. For 

 reasons which cannot yet be fully explained the Triassic period 

 seems to have been one of rapid organic change and development, 

 and in no class is this more beautifully illustrated than in that of 

 the Cephalopoda, the Alpine Trias presenting us with a remarkable 

 assemblage of genera which practically connect the Palaeozoic Gonia- 



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