a, cartilaginous axis of spine ; 6, c, transverse apophyses and ribs; f, 
cranium ; i, A, ocular and nasal cranial cavities; m,n, pedicle by which the mow 
26, bone supporting the lower jaw; 18, 22, palatine cartilages; 0, p, s, cartilages representing 
cranium ; 
the superior maxilla, 
Fig. 500. 
Nei i il 
10 s Ut Me, My, 
\Nisp Y 
es y 
were only a moiety of the posterior division 
e 
is\ 
\ 
\p 
Cartilaginous skull and anterior portion of vertebral column of the Sturgeon ( Accipenser sturio ). 
299 g” , cartilaginous — 
AG AE Mire 
of the fin of the preceding genus. . 
The posterior extremities or ventral fins are 
attached to a zone similar to that which supports 
the pectorals (fig. 500,14). The pelvic zone is, 
however, very incomplete, the superior or iliac 
portion being quite deficient, so that it has n 
connection with the spine, but is simply im: 
bedded among the muscles at the posterior pari 
of the abdomen. ' 
Externally the pelvis supports the first 
of dicrvontat = (fig. 500, 15) 
which is very large, and li ¥ 
long stem (16) composed of r 
rous articulations, to the commen 
ment of which the succeeding 
rays are appended. Inferiorly | 
former is prolonged in the ma 
Rays into a very curious 
Skeleton of Ray. 
1, snout; 2,3, 4, 5, branchial arches; 6, conso- 
lidated anterior vertebre ; 7, humeral apparatus ; 
8, 9, 10, 11, carpus; 12, fin rays; 13, posterior 
detached vertebrz ; 14, pelvic apparatus ; 15, clasp- 
er; 16, tarsus; 17, fin rays of posterior extremities. 
The pectoral fins of the Sharks (fig.496, 497) 
and Sturgeons (fig. 498) are formed after the 
same plan as that of the Skate, only upon a 
considerably smaller scale, representing as it 
shaped a tus called the “clas 
ota ‘ic tai of which we shi 
have occasion to speak further on 
Skeleton of Dermapterygii. 
the cyclostomatous Fishes, such 
the Lamprey, the skeleton is of still more sim 
structure than in the plagiostomatous gent 
The cranium exhibits through life a soft ¢ 
laginous texture; nevertheless it is not dif 
to identify the different pieces of which it ¢ 
sists, and to point out their analogies with 1 
of the osseous Fishes. 
The spine consists of a soft cartilagi 
stem, which along the entire lengt 
the body. It is enclosed in a strong men 
nous investment, from which prolongation: 
given off that perform the office of spinal 
physes; but the only indications of dis 
vertebre exist in the presence of slight 
almost imperceptible rings of osseous subst 
distinguishable upon the surface of the ea 
ginous stem above mentioned. 
The Cyclostomata have neither pectot 
ventral fins, so that in this respect they 
most imperfect of all Fishes: even the ve 
fins situated above and beneath the tai 
only supported by a few soft and scarcely 
sible fibres representing the fin-rays. 
The most remarkable part of the skeleton 
the Lampreys (Petromyzon) is the cartil 
