I think what you mean is a SLUG. Maybe you saw them outside in the garden or the porch recently. Now that the rainy season has arrived they are sure to come out.

A slug is nearly the same as a snail -- except that snails carry coiled shells on their backs, while slugs don't. Slugs and snails belong to the mollusk family and the gastropod class. While the vast majority of gastropods live in water, snails and slugs are the only mollusk class found on land.

Photos of slugs

In the pictures the two long appendages on the head are tentacles, used to feel the snail's environment (what you referred to as antenna). Also, there are two stalked eyes projecting forward and downward from below the tentacles. Slugs can by found in many different sizes shapes and colors, there are at least 40 species of slugs in the US. Size Range is wide.

Common garden slugs are and inch long (this might be the slug you saw). In the Northwest they have banana slugs which are bright yellow, growing from 8 to 18inches! Slugs and snails move by propelling themselves and sending wave after wave of small contractions forward from the back of its foot toward the front.