Boyd’s Bible Dictionary:
(snake). A lizard is meant (Lev. 11:30). The common snail, slug, or slime-snake is meant (Psa. 58:8). Snails abound in the Orient and are not eschewed as a food.
Concise Bible Dictionary:
Snails
In Leviticus 11:30 it is supposed that the word chomet refers to some kind of lizard: the RV has “sand-lizard.” In Psalm 58:8 the word is shablul, of which it says it “melteth.” It was erroneously supposed by the Jews that by the slime which a snail leaves on its trail it gradually wasted away. The passage simply means that when dead the snail seems to melt entirely away: it is used as a symbol of the wicked passing away.