Fugu niphobels (JORDAN et SNYDER) is a small puffer and commonly found in coastal waters Japan. It has a habit of burrowing into the bottom sand. The observatios of this habit were carried out a Murozumi, Hikari City, Yamaguchi Prefecture, in 1964 and 1965. The practical experiments were also performed in the rearing tanks of the Fisheries Research Laboratory, the Faculty of Education, Yamaguchi University. The results are as follows: 1.There are several grounds where many puffers gather and burrow into the bottom sand along the coast of Murozumi. (Fig. 1) 2.The grouds where the puffers burrow into the sand there are granules, which are 125μ-500μ in diameter. 3.When the puffers burrow into the bottom sand, they are crowed. We found 32 individuals per 1 m2 in maximum. 4.The body length of the puffers which are captured at the grounds is 5.8cm-15.3cm. 5.The females caught in the grounds are 1.3-3.0 times as abundant as the males.