Geomalacus anguiformis is a species of air-breathing land slug, a terrestrial pulmonate gastropod mollusc in the family Arionidae, the round back slugs.

This species occurs in south Portugal (Serra de Monchique) and central Spain.

[2] When crawling, the slug has not always a regularly cylindrical shape, there are depressions and dilatations.

[2] Sole is light creamy with darker medial zone, with yellowish or greenish hue.

[2] The reproductive system is diagnostic feature: Geomalacus anguiformis has atrial diverticulum shorter than spermatheca duct[3] while Kerry slug Geomalacus maculosus has atrial diverticulum longer than spermatheca duct.