Japanese rivers and lakes are the habitation of several--seven or eight--species of fresh-water crab (_kani_), which live in holes on the shore and emerge in the daytime, often moving to considerable distances from their homes. Shrimps (_kawa-ebi_) also are found in the rivers and rice-fields. These shrimps as well as a large species of crab--_mokuzo-gani_--serve the people as an article of food, but the small crabs which live in holes have no recognized _raison d'être_. In Japan, as elsewhere, the principal crustacea are found in the sea. Flocks of _lupa_ and other species swim in the wake of the tropical fishes which move towards Japan at certain seasons. Naturally these migratory crabs are not limited to Japanese waters. Milne Edwards has identified ten species which occur in Australian seas also, and Rein mentions, as belonging to the same category, the "helmet-crab" or "horse-shoe crab" (_kabuto-gani_; _Limulus longispina_ Hoeven). Very remarkable is the giant _Taka-ashi_--long legs (_Macrocheirus Kaempferi_), which has legs 1½ metres long and is found in the seas of Japan and the Malay archipelago. There is no lobster on the coasts of Japan, but there are various species of crayfish (_Palinurus_ and _Scyllarus_) the principal of which, under the names of ise-ebi (_Palinurus japonicus_) and _kuruma-ebi_ (_Penaeus canaliculatus_) are greatly prized as an article of diet. Already in 1882, Dunker in his _Index Molluscorum Maris Japonici_ enumerated nearly 1200 species of marine molluscs found in the Japanese archipelago, and several others have since then been added to the list. As for the land and fresh-water molluscs, some 200 of which are known, they are mainly kindred with those of China and Siberia, tropical and Indian forms being exceptional. There are 57 species of _Helix_ (_maimaitsuburi_, _dedemushi_, _katatsumuri_ or _kwagyu_) and 25 of Clausilia (_kiseru-gai_ or pipe-snail), including the two largest snails in Japan, namely the _Cl. Martensi_ and the _Cl. Yoko-hamensis_, which attain to a length of 58 mm. and 44 mm. respectively. The mussel (_i-no-kai_) is well represented by the species _numa-gai_ (marsh-mussel), _karasu-gai_ (raven-mussel), _kamisori-gai_ (razor-mussel), _shijimi-no-kai_ (_Corbicula_), of which there are nine species, &c. Unlike the land-molluscs, the great majority of Japanese sea-molluscs are akin to those of the Indian Ocean and the Malay archipelago. Some of them extend westward as far as the Red Sea. The best known and most frequent forms are the _asari_ (_Tapes philippinarum_), the _hamaguri_ (_Meretrix lusoria_), the _baka_ (_Mactra sulcataria_), the _aka-gai_ (_Scapharca inflata_), the _kaki_ (oyster), the _awabi_ (_Haliotis japonica_), the _sazae_ (_Turbo cornutus_), the _hora-gai_ (_Tritonium tritonius_), &c. Among the cephalopods several are of great value as articles of food, e.g.