OLD RED SANDSTONE. 
281 
rock, we find nothing of that character. The shells which occur in the Old Red, so far as known, 
are quite distinct from those of the Chemung. The most characteristic fossils are the bones 
and scales of fishes. These meet the eye in all localities, from their strong contrast with the 
ground in which they are imbedded, being usually nearly white or bluish in the brownish-red 
rock. These scales and bones are often in minute fragments, and so permeated by iron as to 
offer no contrast in color ; but in other places they are perfect, and from an inch to one and a 
half inches in diameter, appearing like patches of extraneous matter. 
By far the most common of these are the scales of Holoptychus nobilissimus, a fossil well 
known in the same rock in England and Scotland. 
130. 
Scales of Holoptychus nobilissimus and Snuripteris Taylori. 
The enamel of the scale (fig. 2) is marked by large undulating furrows and ridges, which 
become obsolete towards that side covered by the scale next in front. This character alone 
seems sufficient to indicate the fossil. The enamel is often removed from weathering, and 
casts of its outer surface are preserved in the rock. 
Many fragments of bones and some of teeth have been found in the same situation with 
these scales (fig. 4 of woodcut 130 is one of these). Some of the teeth bear a very close 
analogy to the figures of the teeth of Megalichthys. The fragments of bones often resemble 
those of the buckler of Cephalaspis. 
The jawbone with teeth of the following figure were found in the same association. The 
whole length of the jaw was about seven inches. From the prevalence of scales of Holop¬ 
tychus, I had supposed it to belong to that fish, but farther examination has led me to doubt 
the correctness of this opinion. 
[Geol. 4th Dist.] 
36 
