432 THE PERMIAN PERIOD 



the last of many types which had persisted ever since Cambrian 

 times, associated with forms which represent the incipient stages 

 of characteristic Mesozoic types, together with others peculiar to 

 the Permian. 



Plants. — The flora of the Lower Permian is decidedly Palaeozoic 

 in character, and that of the Upper Permian as decidedly Mesozoic, 

 so that if the line dividing these two great eras were drawn in 

 accordance with the vegetation, it would pass through the Per- 

 mian. Even in the Lower Permian, however, the change from the 

 Carboniferous flora is a marked one. The great tree-like Lyco- 

 pods, Lepidodendron and Sigittaria, which were so abundant in the 

 Carboniferous forests, have become very rare ; none of the former 

 genus and only two of the latter have been found in the Upper 

 Barren Measures of Pennsylvania and West Virginia. The Cala- 

 mites continue in hardly diminished numbers and importance. 

 The Ferns are exceedingly abundant and varied, and tree-ferns 

 seem to be more common than they had been before. Especially 

 characteristic genera of these plants are Pecopteris, Callipteris 

 (PL VII, Fig. 5), Cynoglossa, Neuropteris, Sphenopteris (PL VII, 

 Fig. 6), etc. The Gymnosperms mark a notable advance; in ad- 

 dition to the ancient CorJaitcs, are true Cycads (Baiera) and 

 Conifers ; of the latter are found yew-like forms, Walchia, Saportia, 

 with leaves nearly four inches wide, and Gingko. 



In the Upper Permian Lepidodendron, Sigillaria, and Calamites 

 are quite unknown, though probably a few stragglers still existed, 

 and the flora is made up of Ferns, Cycads, and Conifers, the 

 Angiosperms still being entirely absent. 



Ccelenterata. — The Corals are still mostly of Palaeozoic type 

 and belong to Carboniferous genera, but some of the modern 

 Hexacoralla have appeared. 



Echinodermata. — This group has dwindled in the most remark- 

 able way, and instead of the great forests of Crinoids which 

 flourished in the Carboniferous seas, are found only occasional 

 specimens. 



Arthropoda. — The last few stragglers of the genus Phillipsia 

 indicate the extinction of the great Palaeozoic group of Crustacea, 



