708  STRATIGRAPHICAL GEOLOGY. [Boos VI. _ 
stone systems of Western Europe. The abundant marine fauna of 
the Ludlow period entirely disappeared from the region. As soon as 
the red rocks begin, the fossils rapidly die out. Yet that the Upper 
Silurian fauna continued to live on outside of the Old Red Sandstone 
areas is proved by the occurrence of Silurian species of Orthoceras, 
Graptolite, &c., in a zone of the Scottish Old Red Sandstone 5000 feet 
above the bottom of the system. On the land that surrounded the 
lakes or inland seas of the period, there grew the oldest terrestrial 
vegetation of which more than mere fragments are known. It has 
been scantily preserved in the ancient lake-bottoms in Hurope; 
more abundantly in Gaspé and New Brunswick. The American 
localities have yielded to the researches of Principal Dawson of 


i] “2 
=> ff Ge Ur * 
a 
Fic. 331.—PstLopHyton ropustum (DAwson). Lower Oxip Rep Sanpsronn, PEertTH- 
SHIRE. Drawn BY Mr. R. Kinston, 
a, specimen of the plant } nat. size; b, fructification ; c, empty spore-cases. 
Montreal no fewer than 118 species of land-plants. They are 
almost all acrogens, lycopods and ferns being largely predominant. 
Among the distinctive forms the following may be mentioned :— 
Psilophyton (Fig. 331), Arthrostigma, Leptophlewm, and Prototaxites. 
Forty-nine ferns include the genera Palsxopteris (Cyclopteris), 
Neuropteris, Sphenopteris, and some tree-ferns (Psaronius, Caulo- 
pteris). Lepidodendroid and sigillaroid plants abound, as well as 
calamites. Higher forms of vegetation are represented by a few 
