Heterobranchia, the heterobranchs, is a taxonomic clade of snails and slugs, which includes marine, aquatic and terrestrial gastropod mollusks.
Heterobranchia
A shell of the marine species Bulla quoyii, which is an opisthobranch.
Berthella martensi, a pleurobranch.
Gastropods, commonly known as slugs and snails, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda.
Gastropoda
Cepaea nemoralis: a European pulmonate land snail, which has been introduced to many other countries
The shell of Zonitoides nitidus, a small land snail, has dextral coiling, which is typical (but not universal) of gastropod shells.
The upper pair of tentacles on the head of Helix pomatia have eye spots, but the main sensory organs of the snail are sensory receptors for olfaction, situated in the epithelium of the tentacles.