THE OLD RED SANDSTONE. 69 
armed with enamelled osseous scales, of a stony hardness. It 
seems a somewhat curious circumstance, that fishes so unlike 
each other in their internal framework should thus resemble 
one another in their bony coverings, and in some slight degree 
in their structure of tail. One of the characteristics of sau- 
roid fishes is the extreme compactness and hardness of their 
skeleton.* 
It requires skill such as that possessed by Agassiz, to de- 
termine that the uncouth Coccosteus, or the equally uncouth 
Pterichthys, of the Old Red Sandstone, with their long articu- 
lated tails and tortoise-like plates, were bona fide fishes; 
but there is no possibility of mistaking the Osteolepis: it is 
obvious to the least practised eye that it must have been 
a fish, and a handsome one. Even a cursory examina- 
tion, however, shows very striking peculiarities, which are 
found, on further examination, to characterize not this fam- 
ily alone, but at least one half the contemporary families 
besides. We are accustomed to see vertebrated animals 
with the bone uncovered in one part only, —that part the 
teeth, — and with the rest of the skeleton wrapped up in flesh 
and skin. Among the reptiles, we find a few exceptions; 
* «The sauroid or lizard-like fishes,” says Dr. Buckland, “ :ombine 
in the structure, both of the bones and some of the soft parts, charac- 
ters which are common to the class of reptiles. The bones of the 
skull are united by closer sutures than those of common fishes. The 
vertebre articulate with the spinous processes of sutures, like the 
vertebre of saurians; the ribs also articulate with the extremities of 
the spinous process. The caudal vertebre have distinct chevron 
bones, and the general condition of the skeleton is stronger and more 
solid than in other fishes: the air bladder also is bifid and cellular, 
approaching to the character of lungs; and in the throat there is a 
glottis, as in sirens and salamanders, and many saurians.”’ — Note to 
Bridgewater Treatise, p. 274, first edit. 
1 * 
