COMPARATIVE STUDY OF SCOMBROID FISHES. 
307 
fishermen call the albacore “ tombo-shibi ”, meaning the dragon-fly tunny. The 
number of fin-rays in the pectoral is 18 in the genus Scomber, 19-24 in the 
genus Cybium , 25 in Gymnoscirda, 30 - 36 in the Thunnidæ, ca 30 in 
Katsuivonus and Eutliynnus, and ca 25 in Aux is. Thus in general the number 
of fin-rays in the pectoral increases as the structure of the body becomes more 
complicate, and again decreases as the structure degenerates. The expanse of 
the pectoral is nearly unchanged, though the number of rays is increased. 
There is no doubt that the greater number of fin-rays increases the rigidity 
of the fin itself. In the Scombridæ the pectorals are small, triangular, and 
are situated a little higher than in the Cybiidæ and Plecostei. In the 
Cybiidæ the pectorals are also small, often broad at the origin, and more or 
less crenulated at the ventral margin, as in Cybium niphonium, G. guttcitum 
and Gymnoscirda nuda. In Cybium clnnense, however, the pectorals are large, 
and rounded at the posterior margin (fig. 34). The form is quite extra¬ 
ordinary. In the Thunnidæ the pectorals are generally long, reaching the 
origin of the second dorsal, and even pass beyond it. These fins gradually 
tapering behind, are sabre-shaped. In the Katsuwonidæ the pectorals are 
small and triangular. They are pointed at the posterior dorsal end. In 
Sarda and Plecostei a special elastic protuberance or rather a ridge is 
developed at the inner or dorsal side of the root of pectorals to fit tightly to 
a corresponding groove on each side of the body. 
The ventrals are thoracic, moderate in size, always composed of one 
spine and five fin-rays, and as in many other fishes fit to depressions of the 
body when folded. These fins seem to be of secondary importance, as their 
fin-rays remain transversely articulated, and they are reduced in size in the 
Cybiidæ, being smaller than the anal, except in the genus Gymnosarda. 
The dorsal is divided into two, first and second, and the posterior portion 
of the latter is further divided into many finlets. In the Scombridæ the 
number of finlets is generally 5, in the Cybiidæ 6-9, and in the Plecostei 
8 or 9. The first dorsal is never continuous with the second, and is formed 
of several spines which when depressed are wholly received in a groove. The 
tip of the spines of the first dorsal is flexible, and each spine has a hole at 
the proximal end. In the Scombridæ and also in the genus Auxis of the 
Katsuwonidæ, the two dorsals are separated by an interspace from the 
