216 THE OLD RED SANDSTONE. 
spines, hooked like the beak of an eagle; some with spines 
of straighter and more slender form, and ribbed and furrowed 
longitudinally like columns ; some were shielded by an armor 
of bony points; and some thickly covered with glistening 
scales. If many ages must have passed ere fishes appeared, 
there was assuredly no time required to elevate their lower 
into their higher families. Judging, too, from this ancient 
deposit, they seem to have been introduced, not by individu- 
als and pairs, but by whole myriads. 
‘‘ Forthwith the sounds and seas, each creek and bay, 
With fry innumerable swarmed ; and shoals 
Of fish, that with their fins and shining scales 
Glide under the green wave in plumps and sculls, 
Banked the midsea.” . 
The fish-bed of the Upper Ludlow Rock abounds more in 
osseous remains than an ancient burying-ground. The stratum, 
over wide areas, seems an almost continuous layer of matted 
bones, jaws, teeth, spines, scales, palatal plates, and shagreen- 
like prickles, all massed together, and converted into a sub- 
stance of so deep and shining a jet color, that the bed, when 
** first discovered, conveyed the impression,” says Mr. Murch 
ison, “ that it enclosed a triturated heap of black beetles.” 
And such are the remains of what seem to have been the first 
existing vertebrata. Thus, ere our history begins, the exist- 
ences of two great systems, the Cambrian and the Silurian, 
had passed into extinction, with the exception of what seema 
few connecting links, exclusively molluscs, that are found in 
England to pass from the higher beds of the Ludlow rocks 
into the Lower or Tilestone beds of the Old Red Sandstone.* 
* “Upwards of eight hundred extinct species of animals have been 
described as belonging to the earliest, or Protozoic and Silurian period, 
