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"Skeleton of Lampris guttata, showing the interspinous bones, easily recognisable from their dark tint. 
are met with in acanthopterygious Fishes, and 
branched or soft rays, such as are found in the 
Malacopterygii. They are all divided by a 
longitudinal raphé, or suture, into two lateral 
halves, so that each appears to be formed of 
two rays conjoined,—a circumstance -which 
forms an additional argument against these 
parts of the skeleton being dismemberments of 
the vertebre. 
The rays of the caudal fin are always soft 
and articulated ; but in many Fishes some of 
those at its root, both above and below, are 
gradually diminished in size until nothing is 
left of them but the hard part forming the base. 
Skeletons of Chondropterygii.—In the true 
cartilaginous Fishes, such as the Sharks and 
Rays, the bones are always destitute of those 
osseous fibres which give hardness to the skele- 
ton in the preceding races possessing a true 
bony skeleton. Their interior remains perma- 
nently soft and cartilaginous, while their ex- 
ternal surface is strengthened by becoming en- 
crusted with a layer of granular-looking calca- 
reous matter. 
As there is in the Chondropterygii no depo- 
sition of bony particles radiating from ossific 
centres, there can be no division of the cranium 
into distinct bones, nor of course any sutures: 
the whole cranium consists of a single cartilagi- 
nous piece, in which, however, it is easy to dis- 
Fig. 
tinguish the same regions, the same fossz, the 
same eminences, and the same holes as in the 
skull of one of the osseous Fishes; but, although 
it is not difficult with a little attention to point 
out the situation of the different bones, to 
define their limits is impossible. 
The bones of the face are likewise consoli- 
dated with the great cranial mass, and conse- 
quently are quite undistinguishable except from 
their position in relation to organs into the 
composition of which they enter. 
The structure of the skull therefore appears 
exceedingly simple when compared ith that 
of an osseous fish. The whole pterygo-temporal 
apparatus is represented by two pieces, one of 
which corresponding with the temporal, tym- 
panic, symplectic, and jugal bones of Cuvier, 
or the tympanic pedicle, as Professor Owen 
calls the long stem, which in the osseous 
Fishes is composed of those elements, is here 
represented by a single piece (fig. 496, c) in- 
terposed between the side of the cranium and 
the point of junction between the upper and 
lower jaws—an arrangement precisely similar 
to that which is observable in the Batrachian 
Reptiles. 
The other piece belonging to the pterygo- 
temporal apparatus (fig. 496, e) forms, in con- 
junction with its fellow of the opposite side, 
almost the whole of the upper jaw, covering 
496. 
SSS 
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: Anterior portion of the skeleton of a female Shark ( Acanthias niger ). 
a, a, cartilaginous skull; 5, nasal cavity; d, lower jaw; e, upper jaw; f, g, connecting pedicle ; 
1, 2, 3, 4, 5, branchial apparatus ; 6, 4, zone supporting (, /,) pectoral fins. 
3 Q 2 
