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The fishes of this lowest English Old Red are Cephalaspis and Pteraspis, specifically different from species of the same genera which occur in the uppermost Ludlow or Silurian tilestones. Crustaceans also of the genus Eurypterus are met with.
"A world without us!" it says, as a heady young Cephalaspis might have said it in the old Silurian sea. But since the Cephalaspis and the Coccostëus many a fine animal has increased and multiplied upon the earth, lorded it over land or sea without a rival, and passed at last into the night. Surely it is not so unreasonable to ask why man should be an exception to the rule.
Some of the fossils of this system, the cephalaspis, coccosteus, pterichthys, holoptychius are, in form and structure, entirely different from any fishes now existing, only the sturgeon family having any trace of affinity to them in any respect. They seem to form a sort of connecting link between the crustacea and true fishes.
BRITISH. Bituminous schists of Gamrie, Caithness, etc., with numerous fish. BRITISH. Arbroath paving-stones, with Cephalaspis and Pterygotus. FOREIGN. Oriskany sandstone of Western Canada and New York. BRITISH. Upper Ludlow formation, Downton sandstone, with bone-bed. FOREIGN. Niagara limestone, with Calymene, Homalonotus, etc. BRITISH. Bala and Caradoc beds.
So far as our present information goes the Ganoids are as old as the Sharks; and it is very interesting to observe that the remains of the oldest Ganoids, Cephalaspis and Pteraspis, have as yet displayed no trace of jaws. It is just possible that they may connect the Monorhina, with the Sturgeons among the Amphirhina.
Upper Old Red Sandstone in Scotland, with Fish and Plants. Middle Old Red Sandstone. Classification of the Ichthyolites of the Old Red, and their Relation to Living Types. Lower Old Red Sandstone, with Cephalaspis and Pterygotus. Marine or Devonian Type of Old Red Sandstone. Upper Devonian Rocks and Fossils. Middle. Lower. Eifel Limestone of Germany. Devonian of Russia.
Far down in the sandstones of Gaspe, Dr. Dawson found, in 1869, an entire specimen of the genus Cephalaspis, a form so characteristic, as we have already seen, of the Scotch Lower Old Red Sandstone.
The newest of the series is a clay-slate, on which, along the southern borders of the Grampians, the Lower Old Red, containing Cephalaspis Lyelli, Pterygotus Anglicus, and Parka decipiens, rests unconformably.
The number of species of fish already obtained from the middle division of the Old Red Sandstone in Great Britain is about 70, and the principal genera, besides Osteolepis and Pterichthys, already mentioned, are Glyptolepis, Diplacanthus, Dendrodus, Coccosteus, Cheirancanthus, and Acanthoides. Cephalaspis Lyellii, Agassiz. Length 6 3/4 inches.
The cephalaspis may be considered as making the smallest advance from the crustacean character; it very much resembles in form the asaphus of lower formations, having a longish tail-like body inserted within the cusp of a large crescent-shaped head, somewhat like a saddler's cutting-knife.
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