CAEBON-IFEEOUS FATJNA. 153 



these animals should have been foreshadowed in the Devonian dip- 

 teroid ganoids, which, leading up to the lung-flshes on one side, 

 and not impossibly directly to the amphibians on the other, eflEect 

 a transition to the higher class from the side of the fishes. This 

 succession of higher upon lower types is not a matter of accident, 

 but a direct outcome of the inevitable laws of evolution. Through 

 the application of no other law would the numerous accidental or 

 coincidental occurrences of direct succession, which present them- 

 selves throughout the entire geological series, receive an intelligent 

 explanation. All the Carboniferous amphibians belong to the ex- 

 tinct order of the Labyrinthodontia (Stegocephala), salamandroids 

 of both minute and gigantic frame, whose members were distin- 

 guished by the possession of a dermal (cephalo-dorsal and ventral) 

 armour of sculptured plates, and in many cases by a peculiar laby- 

 rinthine infolding of the enamel of the teeth, a structure unknown 

 among modern amphibians, but which is in great part shared by 

 certain members of the ganoid fishes, as the modern alligator-gars 

 (Lepidosteus) and the genus Rhizodus (Carboniferous). Among 

 the genera are Anthracosaurus, Hylerpeton, Dendrerpeton, Batra- 

 chiderpeton, and' the caecilian-like Dolichosoma and Ophiderpeton. 

 No other vertebrate higher in the scale of organisation than these 

 labyiinthodonts is as yet apparent, unless, possibly, the very doubt- 

 ful Eosaunis be proved to be a true reptile. 



The flora of this period partakes essentially of the character of 

 that of the period preceding, the Devonian. We have here the 

 same ancient representatives of the modern club-mosses and horse- 

 tails, the Lepidodendra and their allies,* and the calamites, the 

 ferns — Neuropteris, Pecopteris, Alethopteris, Sphenopteris, Cyclop- 

 teris — giant tree-ferns, and forms that have been referred to the 

 group of the cycads, an order of plants to which the sago-palms 

 belong, and which appear to be not distantly removed from the ■ 

 conifers. No positive indications of the existence of any true 

 flower-bearing herbaceous plants are yet manifest, and with their 

 absence the total absence of flower-frequenting or nectar-sucking 



* The recent anatomical investigations of Eenault and Saporta have led 

 these authorities to consider Sigillaria, at least in some of its recognised forms, 

 to he much more closely related to the gymnospermous phanerogams than to 

 the club-mosses ; but Professor Williamson has pretty definitely shown that 

 such a relationship does not exist. 

 8 



