44 THE LESSON OF EVOLUTION 



them. The Coccosteidce, which lived from the 

 Devonian to the lower Carboniferous, are placed in 

 the Dipnoi by Mr. A. Smith Woodward. They had 

 the anterior portion of the body protected by an 

 armour of large plates, like the Ostracodermi, but 

 their paired fins are unknown , and so could not have 

 been armoured. They had, however, well de- 

 veloped jaws and teeth. 



We will turn now to the land. 



The flora of the Devonian period shows a consider- 

 able advance on that of the Silurian. More than a 

 hundred species are known, including, probably, 

 most of the principal types of Cryptogams as well 

 as true Gymnosperms ; among the former being ferns 

 and Arclnceocalamites , as well as the large crypto- 

 gamic trees, Lepidodendron and Sigillana. 



Owing to the numerous excavations made in coal- 

 mining, we know the flora of the lowlands and 

 swamps of the Carboniferous period remarkably well ; 

 but it is practically the same as that of the Devonian, 

 and was continued with little alteration into the 

 Permiam. Some of the plants e.g., Psilophyton 

 and Ptilophyton cannot be placed in our modern 

 classification, for they are unlike anything living; 

 while, at the same time, they are not sufficiently 

 well known to warrant new orders being made for 

 their reception. Sir J. W. Dawson's opinion that 

 the Rhizocarpetz existed in abundance in Carboni- 

 ferous times has not been confirmed by later obser- 

 vers ; and Sphenophyllum has been placed in a 

 special class, connecting the Equisetacece with the 



