Palaeos		Gastropoda: Pulmonata
Mollusca		Systellommatophora

Systellommatophora

GASTROPODA  
|--Caenogastropoda
`--Heterobranchia
   |--Opisthobranchia
   |
   `--PULMONATA
      |==Basommatophora
      `--+--Stylommatophora
         `--+--Systellommatophora 
            `==Acteophila  

Introduction

The Systellommatophora include several families of slug-like animals that have been continuously shuffled from one taxon to another (Chase, 2002), but don't seem to fit in either the Basommatophora and Stylommatophora. All have the anus located at the posterior end of the body, but the intertidal Onchidiidae have a posterior pulmonary sac, while the tropical Veronicellidae have lost the pulmonate lung.  Barnes (1980).

The Systellommatophora are considered a polyphyletic taxon by Wade & Mordan (2000).

The following classification is from Jeffery 2001

Suborder SYSTELLOMMATOPHORA Otinoidea Otinidae Adams & Adams, 1855 Smeagolidae Climo, 1980 Onchidoidea Onchidiidae Gray, 1824 Rathouisioidea [= Order Soleolifera [Solem 1978]] Rathouisiidae Sarasin, 1899 Veronicellidae Gray, 1840