I have had 2 live P. elegans for almost 2 years, but only recently started paying close attention to them. Here are a series of photographs of how they come out of their shells.
As explained in the previous post about this species, when the snail is completely withdrawn into its shell, its aperture is sealed with a hard, calcareous operculum that is permanently attached to the top of the snail's foot. In A, the operculum is starting to lift up. In B, the red arrow points at the tip of one of the tentacles that is "peeking" out. Unlike most other land snails, the eyes of P. elegans are not at the tips of its tentacles. However, there must be some chemical receptors on the tentacles, perhaps in the darker tips, that the snail seems to be using to check out the outside world before any other part of the body is brought out. Right below the tentacle, you may also notice the tip of the proboscis (it is easily visible in the original high resolution picture). In C, both tentacles and the proboscis are out. Notice that each tentacle is pointing in a different direction, which, again, seems to suggest that the snail is using them to sense the surroundings.
In B and C, the deeply furrowed part to the other side of which the operculum is attached is actually the sole of the foot. In D, the snail has twisted its foot around and is bringing the sole in contact with the ground. The head has also twisted around and is momentarily facing the ground. In E, most of the sole is resting on the ground, the left eye is visible at the base of the left tentacle, but the shell hasn't moved to its proper position yet. Finally, in G, the snail has twisted its shell around to its "cruising" position on top of the operculum. The proboscis in contact with the ground is visible in the front. The snail is ready to push the pedal to the metal!
This seemingly complex set of maneuvers, which is reversed when the snail is withdrawing into its shell, is necessary to protect the head, the most vital part of the snail's body that is exposed to the outside. When a snail senses danger, it withdraws its head into its shell first, followed by the rest of the foot. But, the problem is that before the snail can come back out, it needs to put its tentacles out to determine if it's safe to come out. The snail accomplishes that by doubling over itself within its shell. Another reason why the snail's head needs to be located near the aperture, even though it goes in before the foot, is that the lung and its opening are located in the head.
In this case, unintelligent evolution couldn't come up with a better solution other than turning the snails into contortionists.
Interestingly, the land snails that have lost their opercula during evolution go thru the same sequence when they are withdrawing or coming out of their shells.