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Let it be borne in mind that 'Avicula', 'Mytalis', 'Chiton', 'Natica', 'Patella', 'Trochus', 'Discina', 'Orbicula', 'Lingula', 'Rhynchonella', and 'Nautilus', all of which are existing 'genera', are given without a doubt as Silurian in the last edition of 'Siluria'; while the highest forms of the highest Cephalopods are represented in the Lias by a genus, 'Belemnoteuthis', which presents the closest relation to the existing 'Loligo'.
Though Siluria, in common with other geological works, supplies numerous proofs that rocks of the same age are often of widely-different composition a few miles off, while rocks of widely-different ages are often of similar composition; and though Sir R. Murchison shows us, as in the case just cited, that he has himself in past times been misled by trusting to lithological evidence; yet his reasoning all through Siluria, shows that he still thinks it natural to expect formations of the same age to be chemically similar, even in remote regions.
"What's good enough for Rome," they said, "is surely good enough for Siluria," and, shivering, showed the latest official visitor a landscape that might have been transported bodily from the Sabine Hills ... if only there were more sun! "But we do miss the lizards and the cicalas," they would say with a sigh.
Let it be borne in mind that Avicula, Mytilus, Chiton, Natica, Patella, Trochus, Discina, Orbicula, Lingula, Rhynchonella, and Nautilus, all of which are existing genera, are given without a doubt as Silurian in the last edition of "Siluria;" while the highest forms of the highest Cephalopods are represented in the Lias by a genus, Belemnoteuthis, which presents the closest relation to the existing Loligo.
The student may refer to the excellent tables given in the last edition of Sir R. Murchison's Siluria for a list of the organic remains of all classes distributed through the different subdivisions of the Upper and Lower Silurian.
From the recently-published third edition of Siluria, may be culled numerous facts of like implication. Sir R. Murchison considers it ascertained, that the siliceous Stiper stones of Shropshire are the equivalents of the Tremadock slates of North Wales. Judged by their fossils, Bala slate and limestone are of the same age as the Caradoc sandstone, lying forty miles off.
Throughout his Siluria, Sir R. Murchison habitually assumes that the same, or kindred, species, lived in all parts of the Earth at the same time.
When the vertebrate vanished in Siluria, it disappeared instantly and forever. Neither vertebra nor scale nor print reappeared, nor any trace of ascent or descent to a lower type. The vertebrate began in the Ludlow shale, as complete as Adams himself in some respects more so at the top of the column of organic evolution: and geology offered no sort of proof that he had ever been anything else.
Let it be borne in mind that Avicula, Mytilus, Chiton, Natica, Patella, Trochus, Discina, Orbicula, Lingula, Rhynchonclla, and Nautilus, all of which are existing genera, are given without a doubt as Silurian in the last edition of "Siluria"; while the highest forms of the highest Cephalopods are represented in the Lias by a genus Belemnoteuthis, which presents the closest relation to the existing Loligo.
Let it be borne in mind that 'Avicula', 'Mytails', 'Chiton', 'Natica', 'Patella', 'Trochus', 'Discina', 'Orbicula', 'Lingula', 'Rhynchonella', and 'Nautilus', all of which are existing 'genera', are given without a doubt as Silurian in the last edition of 'Siluria'; while the highest forms of the highest Cephalopods are represented in the Lias by a genus, 'Belemnoteuthis', which presents the closest relation to the existing 'Loligo'.
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