82 THE OLD RED SANDSTONE. 
are so frequently distorted as the Cheiracanthus. It seems to 
have been more a cartilaginous and Jess an osseous fish than 
most of its contemporaries. However perfect the specimen, 
no part of the internal skeleton is ever found, not even when 
scales as minute as the point of a pin are preserved, and 
every spine stands up in its original place. And hence, per- 
haps, a greater degree of flexibility, and consequent distor- 
tion. The body was covered with small angular scales, 
brightly enamelled, and delicately fretted into parallel ridges, 
that run longitudinally along the upper half of the scale, and 
leave the posterior portion of it a smooth, glittering sur- 
face. (See Plate VII, fig. 2.) They diminish in size to- 
wards the head, which, from the faint stain left on the stone, 
seems to have been composed of cartilage exclusively, and 
either covered with skin, or with scales of extreme minute- 
ness. The lower edge of the operculum bears a tagged 
fringe, like that of a curtain. The tail, a fin of considerable 
power, had the unequal sided character common to the for- 
mation; and the slender and numerous rays on both sides 
are separated by so many articulations as to present the ap- 
pearance of parallelogramical scales. The other fins are 
comparatively of small size. ‘There is a single dorsal placea 
about two thirds the entire length of the creature adown the 
back; and exactly opposite its posterior edge is the anterior 
edge of the anal fin. The ventral fins are placed high upon 
the belly, somewhat like those of the perch; the pectorals 
only a little higher. But it is rather in the construction of 
the fins, than their position, that the peculiarities of the 
Cheiracanthus are most marked. The anterior edge of each, 
as in the pectorals of the existing genera Cestracion and 
Chimera, is formed of a strong, large spine. In the Chimera 
borealis, a cartilaginous fish of the Northern Ocean, the 
