雙尾のハコフグ  [in Japanese] A Coffer-fish with Double Caudal Fins  [in Japanese]

A specimen of Ostracion farnasini having double caudal fins is dissected and obtained the following results. The extra-fin is found developing directly from the ventral side of the ventral basal plate of the tail, where the structur of the bone is quite malformed. In the median greater part the striation or the arrangemente of the constitution elements of the bone tends to the ventral as shown in Fig. 2b, instead of antero-posterior of the normal bone (Fig. 2a), and the fin rays develop so far as the extent of this deformed area. They count 10 in number plus a rudimental basal piece. The primary tail fin contains also 10 rays. This number of rays holds through to all normal specimen examined. Therefore, there is no reduction of number of rays both to the primary and the extra-fin. Moreover, 3 more bony pieces like basal piece of ray are found between the two tail fins. Further details can be studied on the accompanying figures, Fig. 1, general view of the fish, Fig. 2, inner structure of the tail fin, a) normal, b) doubled.