(1) The Geological Outline Fossil fishes of the Scombridae were found at Iwayakannon, Sinobuyama in the suburbs of the city of Hukusima. Sinobuyama, a solitary hill in the Hukusima basin, is 273m. high above the sea level, and about 200m higher than the basin floor. It is mostly composed of the massive liparitic tuff, partly agglomeratic, and its lower part of alternation of tuffaceous sands-tone and shale containing plant fossils. The fishes were found associated with plants in a horizon. The stratigraphical relation of this fossil horizon with Ya-nagawa shell bed, north-east of hukusima basin, cannot actually be determined. However, I agree with TSUJITA in that this horizon will be younger than the Yana-gawa shell bed. (2) The Fossils The number of the fossils collected is about 50. These fossils are of the same species. The result of my measurement is shown i-n the table. The length of the fossil is about 40cm, and its form resembles tha-t of Scombridae fish. The body(the caudal fin excluded) is 3.7 times as long as the head; the thickest part of the body is a little posterior to the base of th-e first dorsal fin, and is 0.7 times as long as the head. The height of the hea-d is about half of the length of the head. The pectoral fins consists of 3 spin-ous and 15 soft rays; the length is equal to the distance from the pectoral fins to the base of ventral fins. The ventral fin consists of 7 rays and it is shor-ter than the pectoral fin. The first dorsal fin is above or slightly in front o-f the ventral fin, its spines have 12 soft rays. It has 5 finlets. The anal fin has one spine and 11 soft rays. The caudal fin is about one tenth as long as th-e total length of the fish, and it is deeply forked with 38 rays. The mouth is large, about one third of the head, and both jaws have small teeth. The vertebra-e consist of about 12 abdominal vertebrae and 18 caudal vertebrae. This Scombri-dae fish is distinguished from the present Scomber japonicus HOUTTUYN, (though the two resemble each other) by the fact that the former is more slender than th-e latter, and that the pectoral fins grow more in front than the latter. Recent-ly NIINO, has reported about Scombridae fish is distinguished from the present Scomber japonicus HOUTTUYN, (though the two resemble each other) by the fact tha-t the former is more slender than the latter, and that the pectoral fins grow m-ore in front than the latter. Recently NIINO, has reported about Scombridae fis-h found in Gumma prefecture. Although the precise accounts were not described, the facts that the fossils are found in a great number in one horizon and that t-uff is above the fossil bed, are noted. D.S. JORDAN reported the discovery of the Scombridae fish in Miocene of Southern California, but none of my specimens a-grees with his. This fish is eventually cited as Scomber sp.
View full abstract