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KAMAKICHI KISHINOUYE : 
second vertebra, instead of tbe third. In this family the tips of long anterior 
intermuscular bones overlap each other at the external surface of the lateral muscle. 
In Gybium the intermusclar bones are scarcely developed in the caudal region 
(fig. 6), and the anterior intermuscular bones are turned more or less upward. 
In other scombroid fishes the intermuscular bones almost He in one plane. In 
Scirda intermuscular bones are very well developed. They are thick and long 
in the anterior precaudal region. In Acanthocybium solandri the intermuscular 
bones are ten in number, and are found in the precaudal region only; but in 
Scirda and Gymnosarda they are found in the caudal part too. 
In the Plecostei the ribs are broad, clorsoventrally compressed, and 
gradually attenuated towards the posterior, internal side. They he close to 
each other and do not hang down along the peritoneum, but they thatch the 
roof of the abdominal cavity. In the Thunnidae the proximal portion of 
one or two ribs, lying just before and above the root of the cutaneous 
artery, is very slender, so as not to obstruct the free passage of the blood. In a 
large specimen of Thunnus orientalis I found that the fifth and sixth ribs con¬ 
sist of two parts. The short, slender, proximal part lies at the anterior slope 
of the hypaxial portion of the lateral muscle, which is rather suddenly developed 
from the myotome of the seventh vertebra. These are probably abnormal. 
The intermuscular bones are developed from the cephalic region to the caudel 
region, and they are united to the lateral median line of the vertebral column, 
and each pah at the anterior margin of the centrum of each vertebra, except 
in the first vertebra, in which these bones are attached to the neural arch. 
These bones are long, slender, and their distal ends lie at the external surface 
of the lateral muscle in the anterior part of the body (figs. 2-5) ; but the 
majority of them have their distal end at the boundary between the superficial 
dark red muscle and the profound dark red muscle. The intermuscular bones 
found anterior to the seventh vertebra are long, and appear on the surface of 
the lateral muscle, while those posterior to the seventh vertebra become short 
rather suddenly, and in the case of Katsuwonidae the last two to seven of 
those intermuscular bones are divided into two portions (fig. 5) ; the part 
beyond the profound dark muscle is separate from the proximal part and these 
two pails are connected with a ligament. Intermuscular bones on the third 
and fourth vertebrae are fused to the dorsal side of the head of the respective 
