PISCES. 
vertebree of the spine by a loose ligamento- 
cellular substance. 
In other Sharks and in the Rays (fig. 496, 
1, 2, 3, 4, and fig. 500, 3, 4, 5) the ossification 
of these pieces is very imperfect ; the branchiz, 
in the latter more . 
especially, being al- Fig. 498. 
most entirely sustain- " 
ed by membranous 
structures. 
The pharyngeal 
bones in the true 
Chondropterygii are 
totally wanting. 
In some Sharks, 
as, for example, in 
Galeus, there are ves- 
tiges of a true sternum 
situated below the 
branchial apparatus, 
from the anterior edge 
of which it is sus- 
pended by ligamen- 
tous attachments, 
while posteriorly it is 
connected with the 
centre of the zone, to 
which the pectoral 
fins are attached. To 
the sides of this ster- 
num are appended 
five or six pairs of 
sternal ribs, but the 
ossification of these 
bones, as well as of 
the sternum itself, is 
very incomplete. 
The vertebral co- 
lumn of the cartilagi- 
nous Fishes presents 
two or three very 
remarkable peculiari- 
ties. In the Ray-tribe 
(fig. 500, 6) all the 
vertebre of the ante- 
rior portion of the 
spine for a considera- 
ble distance are im- 
moveably fixed toge- 
ther by an incrusta- 
tion of earthy matter 
that forms a kind of 
tube or sheath in 
which they are en- 
cased, the number of 
vertebre thus anchy- 
losed to each other be- 
ing only indicated b 
the foramina ditough 
which the spinal 
herves make their es- 
cape. 
Another peculiari- 
ty is that both in the 
Sharks and Rays 
there are twice as 
Many superior verte- gheleton of Sturgeon ( Acci- 
bral lamin as there penser Sturio ). 
SSS 
SS 
SS 
we 
SSS 
SM 
SS 
ST 
2 
_——wS 
2 Sy en 
965 
are vertebre. This is owing to the develope- 
ment of spinal laminz to cover the interverte- 
bral spaces, in addition to those which constitute 
the spinal canal in other vertebrata. 
To the transverse processes of the vertebre 
covering the abdomen rudiments of dorsal ribs 
are appended. In the Raide, however, these 
are very small; but in Sharks, (fig. 496, m,) 
and more especially in the Sturgeons (fig. 499, 
6, c,) they attain considerable dimensions. 
Along the whole length of the post-abdo- 
minal region of the vertebral column there 
are developed hemapophysial arches and infe- 
rior spinous processes, but the latter are always 
exceedingly short and imperfectly formed. This 
is well seen in the Sturgeon (fig. 498), in 
which fish, although the central portion of the 
vertebral column remains permanently cartila- 
ginous, the hemapophysial arches and spines 
are distinctly bony. 
There are no interspinous bones, the dorsal 
and anal fins being only connected to the 
spinous processes of the vertebre by broad 
ligamentous expansions. The structure of the 
caudal fin is likewise very different from what 
is met with in the osseous Fishes. In the Sharks 
and Sturgeons, (fig. 498,) which have the tail 
deeply furcate, the vertebral column is conti- 
nued into the upper portion along its entire 
length, the caudal fin being entirely supported 
by long rays connected both superiorly and 
inferiorly to the extremities of the spinous 
processes of the individual vertebre. 
The framework to which the anterior extre- 
mities or pectoral fins are attached is a strong 
osseous zone which encircles the body imme- 
diately behind the branchial apparatus. This 
zone consists superiorly of the scapular and 
supra-scapular pieces, and inferiorly of a broad 
osseous belt (fig. 497, k,) which encloses the 
fore part of the abdominal cavity, representing 
the curacoid and clavicular apparatus of the 
Reptilia. _ In the Raide the supra-scapular 
pieces are inseparably connected with the 
spinous processes of the dorsal vertebra, but 
in the different races of Sharks they are loose 
and unattached. At the junction between the 
dorsal and abdominal portions of the above 
zone are attached by strong articulations the 
pieces which support the rays of the pectoral 
fin. These pieces represent the whole brachial 
and carpal apparatus of the higher Vertebrata. 
In the Rays these are of enormous dimen- 
sions, (fig. 500, 8, 9, 10, 11) extending pos- 
teriorly so as almost entirely to surround the 
cavity of the abdomen, whilst anteriorly they 
are prolonged in a similar manner in front 
of the cranium. To the external aspect of this 
vast carpus are attached upwards of a hundred 
fingers supporting the enormous pectoral fins, 
which here form by far the greater portion of 
the body, giving it that square shape for which 
these Fishes are so reraarkable. Towards the 
circumference of the body each of the fin-rays 
bifurcates (12), so that the total number of 
phalanges entering into the composition of this 
prodigious hand is one of the most remarkable 
facts in comparative osteology. 
