48 THE OLD RED SANDSTONE. 
alarm, and at other times lay close by the creature’s side ; 
and that the sole instrument of motion was the tail, which. 
when covered by its coat of scales, was proportionally of a 
somewhat larger size than the tail shown in the print, which. 
as in the specimens from whence it was taken, exhibits but the 
obscure and uncertain lineaments of the skeleton. The river 
bull-head, when attacked by an enemy, or immediately as it 
feels the hook in its jaws, erects its two spines at nearly right 
angles with the plates of the head, as if to render itself as 
difficult of being swallowed as possible. ‘The attitude is one 
of danger and alarm ; and it is a curious fact, to which I shall 
afterwards have occasion to advert, that in this attitude nine 
tenths of the Pterichthyes of the Lower Old Red Sandstone 
are to be found. We read in the stone a singularly preserved 
story of the strong instinctive love of life, and of the mingled 
fear and anger implanted for its preservation — ** The champi- 
ons in distorted postures threat.” It presents us, too, with a 
wonderful record of violent death falling at once, not on a few 
individuals, but on whole tribes. __ 
Next to the Pterichthys of the Lower Old Red I shall place 
its contemporary the Coccosteus of Agassiz, a fish which, in 
some respects, must have somewhat resembled it. Both were 
covered with an armor of thickly tubercled bony plates, and 
both furnished with a vertebrated tail. ‘The plates of the one, 
when found lying detached in the rock, can scarcely be dis- 
"tinguished from those of the other: there are the same marks, 
as in the plates of the tortoise, of accessions of growth at the 
edges — the same cancellated bony structure within, tne same 
kind of tubercles without. The forms of the creatures them- 
selves, however, were essentially different. I have compared 
the figure of the Pterichthys, as shown in some of my better 
specimens, to that of a man with the head cut off at the 
