. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palaeontological science. Paleontology. THE CARBONIFEROUS PERIOD. 189 In the Devonian rocks we meet with no other remains of Vertebrated animals save fishes only; but the Carboniferous deposits have yielded re- mains of the higher group of the Amphibians. This class, comprising our ex- isting Frogs, Toads, and Newts, stands to some ex- tent in a position midway between the class of the fishes and that of the true reptiles, being distinguished from the latter by the fact Fig. c^c
. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palaeontological science. Paleontology. THE CARBONIFEROUS PERIOD. 189 In the Devonian rocks we meet with no other remains of Vertebrated animals save fishes only; but the Carboniferous deposits have yielded re- mains of the higher group of the Amphibians. This class, comprising our ex- isting Frogs, Toads, and Newts, stands to some ex- tent in a position midway between the class of the fishes and that of the true reptiles, being distinguished from the latter by the fact Fig. c^c/^//^^^«c^«/^r/«^. that its members invariably Carboniferous Limestone, Britain. possess gills in their early condition, if not throughout life; whilst they are separated from the former by always possessing true lungs when adult, and by the fact that the limbs (when present at all) are never in the form of fins. The Amphibians, therefore, are all water- breathers when young, and have respiratory organs adapted for an aquatic mode of life; whereas, when grown up, they develop lungs, and with these the capacity for breathing air directly. Some of them, like the Frogs and Newts, lose their gills altogether on attaining the adult condition; but others, such as the living Proteus and Menobranchris, retain their gills even after acquiring their lungs, and are thus fitted indiffer- ently for an aquatic or terrestrial existence. The name of " Amphibia," though applied to the whole class, is thus not precisely appropriate except to these last-mentioned forms (Gr. af)iphi, both; bios, life). The Amphibians also differ amongst themselves according as to whether they keep per- manently the long tail which they all possess when young (as do the Newts and Salamanders), or lose this appendage when grown up (as do the Frogs and Toads). Most of them have naked skins, but a few living and many extinct forms have hard structures in the shape of scales developed in the integu- ment.
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Keywords: ., bookcentur, bookdecade1870, booksubjectpaleontology, bookyear1876
