The following has been taken, in part, from the preface of Baba's (1949) Opisthobranchia of Sagami Bay.
Sagami Bay is located in about the center of Japan proper, bounded by the Miura Peninsula on the east and by the northern half of the Izu Peninsula on the west. To the south the bay opens far out into the ocean; it is bordered on the north by the hills ranging from Odawara and Oiso to Kamakura and Hayama, of the so-called "River of Shonan."
The depth of the bay varies from the tidal line to 700 meters, and a branch stream of the warm "Kuroshiro" (Black Current) which flows eastward between Oshima Island and the south of the Izu Peninsula, comes into the bay during certain season of the year. Under such local conditions, the water abounds in all sorts of marine fauna and flora, including those characteristic of the southern waters, as many biologist at home and abroad have well recognized. While large numbers of interesting facts about the biological aspect of the bay have already been reported as the result of researches so far carried out by various specialists, it can confidently be anticipated that still more new scientific facts will be disclosed by future investigations.