The Gastropoda class includes snails and slugs found in both aquatic and terrestrial environments. There are three main subclasses - Prosobranchiata which have gills and separate sexes, Opisthobranchiata which have reduced or absent shells and are hermaphrodites, and Pulmonata which breathe through lungs. Pulmonata are further divided into orders including Basommatophora which have one genital opening, Stylommatophora which include land snails and slugs, and Systellommatophora which are tropical slugs. Gastropods play important ecological roles and exhibit tremendous diversity in shell structure, habitat, and reproductive strategies.

2. Gastropoda
The Gastropoda or gastropods, more
commonly known as snails and slugs, are a
large taxonomic class within
the phylum Mollusca
The class Gastropoda
includes snails and slugs of all kinds and all
sizes from microscopic to large
 There are many thousands of species of sea
snails and sea slugs, as well as freshwater
snails, freshwater limpets, land snails and
land slugs

3. Classification of Gastropoda
• There three divisions of the gastropods
regarded by various authors as subclasses
Subclass-Prosobranchiata
• Gills are located anterior to the heart
• The shell aperture is usually with a
calcareous or horny operculum
• There respiration is through gills and the
sexes are separate
• This sub class contains majority of the
gastropods-marine, fresh water and land
snails

4. Classification of Gastropoda
The subclass is divided into three orders
1. Order-Archaeogastropoda
• Each snail has two auricles, two internal gills
and two kidneys
• The gonads discharge through the right
kidney directly into water
2. Order-Mesogastropoda
• One auricle, one gill and one kidney
• The gonad open independently through a
separate genital tract
• The shell is sometimes provided with a
siphonal canal

5. Classification of Gastropoda
3. Order-Neogastropoda
• The snail belonging to this order are same as
the mesogastropods except that a more or
less elongated siphonal canal of the shell
Families under Prosobranchiata are divided
into three categories-

6. Hydrobiidae (Amnicola) Assimineidae (Assiminea grayana) Thiaridae (Thiara)
Pilidae (Pila)Viviparidae (Viviparous)Pleuroceridae (Pleurocera)
1. Freshwater Snail

7. Neritidae (Neritina) Potamidae (Pirenella) Littorinidae (Littorina)
Muricidae (Urosalpinx)Nassariidae (Nassarius)Conidae (Conus)
2. Brackish water and Marine Snail

8. Helicinidae (Helicina) Truncatellidae (Truncatella)
Pomatiasidae (Opisthosiphon)
3. Terrestrial Snail

9. Classification of Gastropoda
Subclass-Opisthobranchiata
• The gill when present is posterior
to the heart
• The shell is reduced or absent
and calcareous spicules are
present in naked forms
• The opisthobranchs are
hermaphrodite and live among
seaweeds and under rocks

10. Classification of Gastropoda
Subclass-Pulmonata
• They have no gills
• The shell when present , is usually in the
form of a simple , regular spire, which
may be only rudimentary
• The Pulmonates are hermaphrodites
There are three subdivision of pulmonates
that are regarded as orders-
1. Order-Basommatophora
• They possess one pair of contractile
tentacles with eyes at the bases
• The shell is conical, discoidal or
patelliform

11. Classification of Gastropoda
• Male and female genital tract
open separately to the exterior

12. Planorbidae (Biomphalaria) Lymnaeidae (Lymnaea)
Physidae (Physa)Ancylidae (Ferrissia)
1. Freshwater Snail

13. Carychiidae (Carychium) Ellobiidae (Melampus)
Gadiniidae (Gadinia)Siphonaridae (Siphonaria)
2. Terrestrial Snail
3. Brackish Water and Marine Snail

14. Classification of Gastropoda
2. Order-Stylommatophora
• The member of this order are land snails
and slugs
• Each specimen possess two pairs of
tentacles, with eyes at the tips of the
posterior tentacles
• The land snail possess well developed
and conspicuous shells while the slug
possess rudimentary concealed shells or
have no shells
• The head-foot region of the land snails is
covered with scales

15. Helicidae (Helix) Helicellidae (Hygromia) Bradybaenidae (Bradybaena)
Succineidae (Succinea)Endodontidae (Anguispira)Polygyridae (Polygyra)
1. Terrestrial Snail

16. Bulimulidae (Bulimulus) Cionellidae (Cionella)
Zonitidae (Zonitoides)Helminthoglyptidae (Cepolis)
1. Terrestrial Snail (Cont…..)

17. Limacidae (Limax) Philomycidae (Philomycus)
Arionidae (Arion)
2. slugs

18. Classification of Gastropoda
3. Order-Systellommatophora
• This order includes those species of slugs
that are mostly tropical
• The members of this order possess two
pairs of contractile tentacles, with eyes
at the tip of the posterior pair
• These slugs have neither an external nor
an internal shell
Veronicellidae (Veronicella)

19. Refference:
• https://en.wikipedia.org/wiki/Snail
• Geerat Vermeij, The Geography of
Evolutionary Opportunity: Hypothesis
and Two Cases in Gastropods;
Integrative and Comparative Biology
42(5):935-40 • November 2002
• http://bioweb.uwlax.edu/bio210/2011/all
sop_dani/classification.htm
http://animaldiversity.org/accounts/Gast
ropoda/
• https://images.search.yahoo.com/yhs/sear
ch?hspart=iba&hsimp=yhs-
1&type=sdnt_5344_CRW_BD&p=pila+snail