THE OLD RED SANDSTONE. 83 
“spine seems placed in front of the weaker rays, just, if I may 
be allowed the comparison, as, in a line of mountaineers en- 
gaged in crossing a swollen torrent, the strongest man in the 
party is placed on the upper side of the line, to break off the 
force of the current from the rest. In the Cheiracanthus, 
however, each fin seems to consist of but a single spine, with 
an angular membrane fixed to it by one of its sides, and at- 
tached to the creature’s body on the other. Its fins are masts 
and sails —the spine representing the mast, and the mem- 
brane the sail ; and it is a curious characteristic of the order, 
that the membrane, like the body, of the ichthyolite, is thickly 
covered with minute scales. The mouth seems to have 
opened a very little under the snout, as in the haddock; and 
there are no indications of its having been furnished with 
teeth.* 
An ichthyolite first discovered by the writer about three 
years ago, and introduced by him to the notice of Agassiz 
during his recent visit to Edinburgh, but still unfurnished with 
a name,t is a still more striking representative of this order 
than even the Cheiracanthus. It must have been proportion- 
ally thick and short, like some of the tropical fishes, though 
rather handsome than otherwise. (See Plate VIII., fig. 1.) 
The scales, minute, but considerably larger than those of the 
Cheiracanthus, are of a rhomboidal form, and so regularly 
striated — the strie converging to a point at the posterior ter- 
mination of each scale—that, when examined with a glass, 
the body appears as if covered with scallops. (See Plate 
* There have been three species of Cheiracanthus determined — C, 
microlepidotus, C. minor, and C, Murchisoni. 
+ Now determined to be a species of Diplacanthus — D. longis 
pinus. . 
9 
