Characteristics of order –Archaeogastropoda of sub class PROSOBRANCHIA

1) They are the Prosobranchia without proboscis, siphon,penis  

    and prosrratic glands.

2) Operculum is also present in many forms with few exception.

3) They have one or two bipectinate internal gills.

4)  They have heart mostly with two auricles.

5)  They usually have two osphradia.

6)  They have two nephridia.

7)  They have nervous system which is not concentrated and usually with two pedal cords.

8) They discharge the sex cells directly into the sea by the right nephridia.
Examples:-Haliotis, Fissurella, Acamaea, Patella, Trochus, Asteraea. Turbo.
        

Fissurella volcano

Patella

Trochus snail