MANUAL OF NATURAL HISTORY. 561 



its flora somewhat the aspect of that of New Hol- 

 land. The curious arborescent fern, Anomopteris, 

 the coniferous genera Voltzia and Thuia, the pal- 

 maceous Oupressites, and the flowering genera of 

 JZthophyllum, Echinostachys, and Palceoxyris, also 

 occur among the vegetable remains of this period. 



II. — Lias Group. 



This is a group of marine argillaceous limestones, 

 stratified blue clays, alum shales, marls, and sand- 

 stones. 



It extends throughout a great part of Europe ; 

 on the Continent, it occurs in the north and south- 

 east of France, in Switzerland, and in Germany ; 

 and it forms a belt across our island, from Lyme- 

 Regis in Dorsetshire to the north of Whitby. 



The Lias was a marine deposit, of which the 

 epoch was remarkable as the " age of reptiles " 

 gigantic saurians having then maintained possession 

 of the shallow ocean, preying on the legions of 

 cephalopods and other mollusks, and swimming 

 around the muddy shores of the half-formed land. 



The remains of the marine, air-breathing, cold- 

 blooded Ichthyosauridce, organized entirely for an 

 aquatic existence, were especially numerous in the 

 Liasic period of the secondary formations. Among 

 the principal genera may be mentioned the Fish- 

 Lizard, or Ichthyosaurus, with its short neck, great 

 eyes, and reptilian head ; and the Plesiosaurus, 

 with crocodile's teeth, serpent's neck, and porpoise's 

 paddles. The fishes comprise many ganoid genera, 



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