Superorder Systellommatophora Mantle cavity absent; anal and usually nephridial opening at posterior; male gonopore behind right tentacle; female gonopore middle of right side; sole of foot narrow; no shell; 2 pairs of retractile, or invaginable, tentacles; marine (Onchidiidae), terrestrial and herbivorous (Veronicellidae), or terrestrial and carnivorous…
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