The doctrine of descent and Darwinism . nplaces, a more smiling appearance. Here begins thefirst record of terrestrial plants. As to the character ofthe fauna, the rapid decrease of the Trilobites is worthyof notice, and the appearance of the important genusof the Cephalopoda, Clymenia, subsequently replacedby the Ammonites. Above all, we must note theincreased abundance of fish which still form the solerepresentatives of the Vertebrata, and held undisputedsway in the seas of that period. Besides the sharks, thereare the mailed Ganoids. It is true, the fish, the hinderpart of which is here por
The doctrine of descent and Darwinism . nplaces, a more smiling appearance. Here begins thefirst record of terrestrial plants. As to the character ofthe fauna, the rapid decrease of the Trilobites is worthyof notice, and the appearance of the important genusof the Cephalopoda, Clymenia, subsequently replacedby the Ammonites. Above all, we must note theincreased abundance of fish which still form the solerepresentatives of the Vertebrata, and held undisputedsway in the seas of that period. Besides the sharks, thereare the mailed Ganoids. It is true, the fish, the hinderpart of which is here portrayed (Fig. 11, Palseoniscus),belongs only to the upper Coal and Zechstein formation ;but it is necessary even now to point out the character-istics of the true Ganoids which floundered about theSilurian seas in somewhat extraordinary forms. Agassiz 72 THE DOCTRINE OF DESCENT. terms them Placoids, from the rhombic scales, providedwith a layer of enamel highly favourable to preserva-tion, and covering the whole surface in oblique The vertebral column, as in the sharks, enters the upperflap of the tail and renders it strikingly Ganoids are, as comparative anatomy has provedwith certainty, a development of the shark-like fishes, ifnot decidedly of a higher grade. The Ganoids, there-fore, presuppose the shark. The carboniferous period owes its name to the enor-mous accumulation occurring in its midst, of theremains of terrestrial plants, fern-like Calamites, andmore especially of Sigillaria and Lepidodendra, stand-ing between vascular Cryptogams and Conifers. Theyformed tropical bog-forests, such as Franz Unger someyears ago attempted to restore in an ingenious compo-sition. In these steaming primaeval forests, differingfrom the early beginnings of antecedent periods bytheir extent and luxuriance, new phases of animallife become manifest—scorpions, myriapods, and in-sects—in other words, air-breathing Articulata, andlikewise the first air-breathing Ver
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Keywords: ., bookauthorschmidtd, bookcentury1800, bookdecade1880, bookyear1882
