In England the word "snail" in popular language is associated with Gasteropods which inhabit land or fresh water, and which possess large conspicuous spiral shells; terrestrial Gasteropods, in which the shell is rudimentary and concealed, are distinguished as "slugs."
Marine Gasteropods are occasionally termed "sea-snails," and the compounds "pond-snails," "river-snails," "water-snails" are in common use.
Schrenck in the north of the Japanese Sea led to the discovery of no fewer than 256 species (Gasteropods, Brachiopods and Conchifers).
This idea originated in the discovery of a jelly-fish, gasteropods, and other organisms of a more or less marine type, and presenting some affinity with forms of Jurassic age.
Pelecypods among the true mollusca were increasing in numbers and importance (Aviculopecten, Posidonomya); Nucula, Carbonicola, Edmondia, Conocardium, Modiola, Gasteropods also were numerous (Murchisonia, Euomphalus, Naticopsis).