. Elements of geology : a text-book for colleges and for the general reader. Geology. Fig. 579.—Jaw of Dendrerpeton Acadeanum, and Section of Tooth, enlarged (after Dawson). Fig. 580.—Section of Hollow Sigil- laria Stump, filled with Sand- stone (after Dawson). posited within the hollow. These sands are rich repositories of organic remains. We can easily imagine the circumstances under which the Dendrerpeton was preserved. A dead Sigillaria tree, rotted to the base and only its hollow stump remaining, stood on the margin of a coal -swamp ; river-floods filled the stump with sand; in the stump
. Elements of geology : a text-book for colleges and for the general reader. Geology. Fig. 579.—Jaw of Dendrerpeton Acadeanum, and Section of Tooth, enlarged (after Dawson). Fig. 580.—Section of Hollow Sigil- laria Stump, filled with Sand- stone (after Dawson). posited within the hollow. These sands are rich repositories of organic remains. We can easily imagine the circumstances under which the Dendrerpeton was preserved. A dead Sigillaria tree, rotted to the base and only its hollow stump remaining, stood on the margin of a coal -swamp ; river-floods filled the stump with sand; in the stump lived and perished a Dendrerpeton ; or else, more probably, the dead body of the reptile, together with shells and other organic remains, was floated into the hollow stump and buried there. This reptile was probably a Labyrin- thodont, but with strong alliances with true reptiles, especially Lacertians. 3. Archegosaurus {Primordial Saurian).—In the Bavarian Coal- measures has been found the almost perfect skeleton of a reptile, about three and a half feet long, which combines in a remarkable degree the characters of Amphibians with those of Ganoid Fishes. It seems to have been a Labyrinthodont Amphibian, with general form and struct- ure adapted for a purely aquatic life. It had, certainly in the early stages of its life, probably throughout life, both gills and lungs, and therefore, like all the Amphibians of the present day at this stage, or like Perennibranchiate Amphibians throughout life, breathed both air and water. The locomotive organs were paddles, adapted for swim- ming, not for walking. The body was covered with imbricated ganoid scales (Fig. 581, A), and the head with ganoid plates. The structure. Fig. 581.—Archegosaurus. of the teeth (B) was also ganoid. The bodies of the vertebra? were not ossified nor even cartilaginous, but retained the early embryonic, fibrous condition of a notochord, It was apparently a connecting link. Please note that these images a
Size: 3084px × 811px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1892
