THE OLD RED SANDSTONE. 65 
have observed, in the cases of a museum of Natural History, 
preparations of fish of two several kinds — preparations of 
the skeleton, in which only the osseous parts are exhibited, 
and preparations of the external form, in which the whole 
body is shown in profile, with the fins spread to the full, 
and at least half the bones of the head covered by the skin 
but in which the vertebral column and internal rays are want- 
ing. Now, in the fossils of the chalk, with those of the other 
later formations, down to the New Red Sandstone, we find that 
the skeleton style of preparation obtains ; whereas, in at least 
three fourths of the ichthyolites of the Lower Old Red, we find 
only what we may term the external style. I had marked, 
besides, another circumstance in the ichthyolites, which 
seemed, like a nice point of circumstantial evidence, to give 
testimony in the same line. The tails of all the ichthyolites, 
whose vertebral columns and internal rays are wanting, are 
unequally lobed, like those of the dog-fish and sturgeon, (both 
cartilaginous fishes,) and the body runs on to nearly the ter- 
mination of the surrounding rays. ‘The one-sided condition 
of tail exists, says Cuvier, in no recent osseous fish known to 
naturalists, except in the bony pike—a sauroid fish of the 
warmer rivers of America. With deference, however, to so 
high an authority, it is questionable whether the tail of the 
bony pike should not rather be described as a tail set on 
somewhat awry, than as a one-sided tail. 
All these peculiarities I could but note as they turned up be- 
fore me, and express, in pointing them out to a few friends, a 
sort of vague, because hopeless, desire, that good fortune 
might throw me in the way of the one man of all the world 
best qualifiea to explain the principle on which they occurred, 
and to decide whether fishes may be at once bony and 
cartilaginous. But that meeting was a contingency rather to 
