400 THE DEVONIAN PERIOD 



same general type as that whose scanty traces are found in Silu- 

 rian strata. All the higher Cryptogams are represented, and by 

 large, tree-like forms, as well as by small herbaceous plants. The 

 bulk of the flora is composed of Ferns, Lycopods (especially the 

 great tree-like Lepidodendrids) , and Equisetaceoe. Rhizocarps, 

 which are now almost extinct, were then abundant. Besides 

 these Cryptogams, we find representatives of the lower kinds of 

 flowering plants in the Gymnosperms, including the Cycads and 

 perhaps the Conifers, which presumably grew upon the higher 

 lands. We shall meet this same flora in richer and more varied 

 display in the Carboniferous period. 



Foraminifera and Sponges are not conspicuous elements of the 

 Devonian fauna. 



Coelenterata. — The Graptolites, which were so abundant in 

 the Ordovician and had become much less common in the 

 Silurian, are now almost extinct, only a few simple species 

 occurring in the Lower Devonian. The Corals, on the con- 

 trary, expand and multiply enormously both in numbers and in 

 size. Most of the Silurian genera persist (though the chain- 

 coral Halysites has become extinct), and many new forms are 

 added. Heliophyllum (PI. IV, Fig. i) is an example of the soli- 

 tary corals, and Plrillipsastrcea and Acervularia (IV, 2) of the 

 reef-builders. 



Echinodermata. — The Cystids have become much rarer than 

 before, and are on the point of extinction ; the Blastoids are still 

 in the background, and the Echinoids have not yet become com- 

 mon ; but the Crinoids and Star-fishes have greatly increased in 

 number and variety. Important genera of the former group are 

 Cupressocrinus, Platycrinus, Actinocrinus, etc. The multitude of 

 the crinoids contributed largely to the building up of the calca- 

 reous sea-bottom on which they flourished. 



Arthropoda. — The Trilobites had already begun to decline in 

 the Silurian, while in the Devonian the decline had become very 

 much more marked, though they were still far from rare. New 

 species of Silurian genera, like Phacops (IV, 12), Bomalo?iolus 

 (IV, n), Lichas, Acidaspis, etc., are the commonest. A character- 



