COMPARATIVE STUDY OF SCOMBROID FISHES. 
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this ligament under the name of the clavicular ligament. It is inserted to the 
inner side of the supraclavicle at one end, and to the occipital region or to 
one of the anterior vertebrae at the other. Another ligament, commonly found 
in the teleostean fishes is long, situated in the spinal canal, above the spinal 
cord, thus connecting the vertebrae. A short median ligament connecting the 
skin in the head to the frontals is peculiar to the Thunnidae. A pair of 
thin and short ligaments is found between the first and second vertebrae in the 
genus Auxis. Besides these there are many ligaments connecting different 
parts of the skeleton. 
Tendons are well developed near both ends of the body, especially near 
the tail, and in the fishes of the Katuwonidae. A longitudiual tendon running 
from the tail and forming the axis of a large muscular cone is very long in 
Auxis (fig. 2). In this genus two tendons forming the anterior extremities of 
the two hypaxial cones of myotomes just below the median septum between 
the epaxial and hypaxial portions of the lateral muscle are remarkable. The 
external tendon is attached to the supraclavicle, just behind the attachment of 
the clavicular ligament, and the internal to the large lateral tubercle of the 
second vertebra. Between every two body-segments we find a pair of tendons. 
These tendons connect the intermuscular bones, and are joined at the abaxial end 
to the myocommata. In the teleostean fishes these tendons are simple, but in 
the plecostean fishes they are longer and much more complicated, as they 
make more acute angles with the vertebral column. 
NERVOUS SYSTEM AND SENSE ORGANS. 
The brain-cavity of the scombroid fishes is small as in other teleo- 
stomatous fishes, and the brain does not occupy even the whole of this small 
cavity, being surrounded by a thick layer of a fatty substance. Thus even a 
tunny of ca 40 kg has a brain as small as a man’s thumb. The brain of the 
scombroid fishes does not differ much from the common type of the brain of 
the Teleostomi. The enormous development of the optical lobe and cerebellum 
is striking. The nondevelopment of the cerebral hemisphere is also remarkable. 
In the Plecostei the optical lobe has a very large groove on the ventral side, 
as if the lobe is made by folding, when seen from that side. The groove is 
especially remarkable in Auxis, in which a corresponding groove is found in the 
