characteristics of class -SCAPHOPODA of Mollusca

The word Scaphopoda is derived from two Greek words.They are scapha=boat and podos=foot. So it includes molluscas having boat shaped body. However the characteristics can be listed as below.
1)They are exclusively marine animals.
2) They have bilaterally symmetrical, elongated body and enclosed in a tusk-like shell open at both ends.
3) They do not have eyes, tentacles and gills.
4) They have tubular Mantle completely enclosing the body.
5) They have mouth surrounded by lobular process or outgrowths.
6) They have reduced foot used for digging .
7) They have rudinmentary heart.
8) They have sexes in separate bodies.
      Example:-Dentalium 

Orders of subclass3-PULMONATA

The subclass 3-Pulmonata has only two orders namely as follows.
Order 1:-BASOMMATOPHORA
  Order 2:-STYLOMMATOPHORA


Order 1:-BASOMMATOPHORA 
          1) They are found in marine water, freshwater and brackish
              water.
          2) They have delicate shell with a conical spire and large
               aperture.
         3) They have one pair of non-invaginable tentacles with the   
          eyes at their bases.
         4) The male and female gonopores are generally separate.
               Examples:- Siphonaria, Lymnaea, Planorbis

ventral surface of Siphonaria

Siphonaria in garden

Dorsal structure of Siphonaria

                                          

planorbis

Lymnaea

Lymnaea

Order2:-STYLOMMATOPHORA
       1) They are terrestrial pulmonates.
         2) They have shell with a conical spire, internal or absent.
         3) They have two pairs of invaginable or retractile tentacles
             with the eyes at the tips of the posterior pairs.
         4) They have male and female gonopores usually united.
             Examples:- Limax, Helix, Partula, Retinella.

limax

Partula

Retinella.

              

characteristics of subclass 3-PULMONATA

1) They are mostly fresh water or terrestrial and few marine .
2) They have typical spiral shell or reduced or absent.If present 
    partly or completely concealed by mantle.
3)They donot have operculum.
4) They have mantle cavity transformed into a pulmonary sac with
   a narrow pore on the right side . Gill is absent.
5) They have heart with one auricle anterior to the ventricle.
6) They are hermaphrodite.