HUXLEY, ON THE SKELETON OF FISHES. 37 
coalesced so as to form a vertical fan-like plate. In these, 
as well as in the bony Ganoids mentioned above, the canal 
for the spinal cord, so soon as the vertebrz cease, passes 
back above the undivided chorda, and both are invested by a 
common case of solid cartilage, which takes the form of a 
long cone. It is a further peculiarity of the Teleostei in 
question, whose caudal rays, with the exception of the upper 
short ones (‘stiitzen strahlen’), are altogether beneath the 
vertebral column, that their terminal vertebra is biconcave. 
The vertebral arches unite in pairs, and form by their proper 
elongation a double spinous process. In one part of these 
fishes (whose ancestors made their appearance in the Jurassic 
epoch) the arches are wedged into pits in the bodies of the 
vertebre (as in Thryssops, Tharsis, Leptolepis, Chirocentrites, 
Elops, Butirinus, Salmo, Coregonus, Saurus, Sudis, Esoz, 
Umbra). In the others, which only appear subsequently in 
the Chalk, the vertebral arches, and even the roof-like bones, 
are inseparably united with the bodies of the vertebre 
(Clupeide, Cyprinide, Cobitis). 
“In the great multitude of the remaining Teleostei, the 
end of the vertebral column is far more developed. The 
chorda is ossified to its extreme end, or crystallized into ver- 
tebree, the last of which, therefore, possesses. only a single 
funnel-shaped cavity, containing the end of the chorda, and 
turned forwards. But in the greater number of these 
Teleostei, whose ancestors made their appearance contempo- 
raneously with the second division of the first-mentioned 
roof-tailed fish in the Chalk, the spimal canal alone is pro- 
longed behind the last vertebral arches, as a bivalve or 
tubular bony sheath, between the fin-rays. These are the 
Percide, Scorpenide, Scienide, Chromide, Sparide, Squami- 
pennes, Teuthide, Labyrinthiformes, Scombrede, Pecilia, 
Characine, Mormyride, Siluroidet, and others. The smaller 
number began to exist an epoch later, with the tertiary forma- 
tions, and in these only does the spinal marrow end at the 
same time with the chorda in the last vertebral body, or at 
least in an inseparable process of it (Labride, Gadide, Blen- 
nide, Gobiide, Pediculoti, Pleuronectide, Lophobranchii, 
Plectognathi, and others).” 
I have omitted Heckel’s account of the vertebral column 
of the Pycnodonts which precedes the long and important 
extract here given, as less immediately germane to the present 
subject. Suffice it to say, that he admits altogether three 
modes of termination of the chorda dorsalis: 1. The end is 
naked or unprotected by any ossification, as in Palzeozoic 
Fishes and existing Ganoidei. 2. Its unossified end is pro- 
