. The testimony of the rocks; . around by a simple con-tinuous margin: and no sooner was the division effectedthan it was found to cast a singularly clear light on theearly history of the class. The earliest fishes — firstbornof their family — seem to have been all placoids. TheSilurian System has not yet afforded trace of any other ver-tebral animal. With the Old Red Sandstone the ganoidswere ushered upon the scene in amazing abundance; and foruntold ages, comprising mayhap millions of years, the entireichthyic class consisted, so far as is yet known, of but these * Here, as in the former dia
. The testimony of the rocks; . around by a simple con-tinuous margin: and no sooner was the division effectedthan it was found to cast a singularly clear light on theearly history of the class. The earliest fishes — firstbornof their family — seem to have been all placoids. TheSilurian System has not yet afforded trace of any other ver-tebral animal. With the Old Red Sandstone the ganoidswere ushered upon the scene in amazing abundance; and foruntold ages, comprising mayhap millions of years, the entireichthyic class consisted, so far as is yet known, of but these * Here, as in the former diagrams (Figs. 1 and 4), the horizontal linesrepresent the divisions of the great geologic systems; while the verticallines indicate the sweep of the several orders of fishes across the scale, andthe periods, so far as has yet been determine^, of their first occurrence lacreatioiL 94 THE PALiEONTOLOGICAL two orders. During the times of the Old Red Sandstone,of the Carboniferous, of the Permian, of the Triassic, and i-ig. AMBLYPTERUS MACROPTERTTS. From the Coal at SaarbracK:.(A Ganoid of the Carboniferous System.) of the Oolitic Systems, all fishes, though apparently as Fi^. 55.
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