Marvels of the Universe 739 
sturgeons, herrings, salmon, and the like, as well as from all other vertebrated animals, in some very 
remarkable features, the most remarkable, perhaps, being the complete absence of limbs and of a 
lower jaw. The lampreys, indeed, are supposed to have branched off from the vertebrate line of 
descent before these important organs had been acquired ; and it may be explained in passing that 
the limbs of the higher vertebrates are represented in all typical fishes by the two pairs of fins on the 
lower surface of the body. 
These preliminary remarks about the lamprey are a necessary introduction to an account of 
the fishes of the Old Red Sandstone, because at the exceedingly remote period—and no one can guess 
within a few million years how remote it was—when the rocks of that geological system were laid 
down on the bottom of the then existing seas or fresh-water lakes, there lived some marvellous fish- 
like creatures which seem to have been related to the lampreys, inasmuch as they appear from the 
available evidence to have possessed neither limbs nor lower jaws. Nevertheless, in one important 
particular at least these ancient fishes differed widely from the soft-skinned lampreys, namely, in 
having the fore part of the body and head protected by a durable and sometimes elaborately con- 
structed investment of armour; and it is to this armour that their preservation in the sedimentary 
rocks is due, and from this that their scientific name, Ostvacodermi, or oyster-skinned, has been 
derived. 
Without entering further into the classification of the Oyster-skinned Fishes, it may be said 
that they belong to, or may be grouped around, three main types, known as the Wing-shield, the 
Helmet-bearer, and the Winged Fish. The Wing-shield, which has been found in the Upper 
Silurian or Lower Old Red Sandstone of Herefordshire, was about six inches long, and seems to 
have been somewhat torpedo-shaped. The hinder part of the body is believed to have been covered 
with rhomboidal scales, while the forepart, which had a pointed snout, carried a dorsal plate, ending 
behind, at all events in some species, in a sharp, backwardly-directed spine; there was a ventral or 
breast-plate as well, and an eye was set on each side of the head. The shape of this fish, which 
has been claimed to be the earliest vertebrate yet discovered, suggests that it was a rapid swimmer ; 
but an allied form, known as the Sickle-shield, was apparently rather a crawler than a swimmer, 
if we may judge from the great width of the body with its nearly square-cut angles, straightish 
FISHES OF THE OLD RED SANDSTONE. 
A side view of Coccasteus shown on the opposite page; it belongs to an ancient group of armoured lung-fishes. It is 
from this group that the higher creatures originated, the stages being Amphibian, Reptile, and, from the Reptiles, Mammals 
and Birds. 
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