What is a snail enclosure?

I thing that the concept behind the 'snail' is a closed transmission line.
The idea is to keep the rear emission of the speaker totally under control, by 'killing' all soundwaves within the box before they reflect and return to hit the speaker's diaphgram.
The cost is a big volume and, like a sealed box, the total loss of the rear emission (that is instead tuned and used as bass reinforcement in the classic open TL)
The snail shape is probably the 'best way of bending' the transmission line, in order to optimize the space occupied and avoid sharp angles in the line.