I recently recieved an interesting cactus from my aunt, and I have absolutely no clue what it is. I don't have a picture, but I can provide a detailed description of it.

The cactus is currently around 2.5 to 3 inches tall and 1.75 inches wide. It has 8 not-very-pronounced ribs, and the same number of folds or creases in between the ribs. Also, there are diagonal "wrinkles" running from the central creases to the ribs on either side. The root system is rather weak, or it has been planted too high, because it is pretty loose and wobbly in the soil. There are absolutely no spines whatsoever. No central spines, no radial spines, no hairs or glochids, nothing. There are areoles (which look like very small brown bumps) on the ribs, evenly spaced about 1 millimeter apart; even the areoles (which normally sprout spines) coming out of the apex are spineless, which means they couldn't have been rubbed or scraped off. My aunt says it has often produced flower buds (in fact, it has one right now) but that they have never opened. I don't know if this is a cultivation error or a characteristic of the plant. The shape is ovoid, about twice as high as tall. The coloring is a grayish green, with alternating light and dark horizontal stripes, as if alternating moist and dry periods cause the growth point to be a lighter or darker color. It's sort of like tree rings, I guess, but on the outside. Anyways, back to the description. The bottom 3/4 inch or so has turned brown and woody (not rotten, but lost chlorophyll and hardened, kind of like a tree trunk) and the ribs on this section have flattened out to become flush with the rest of the surface. This suggests to me that the cactus is rather old, as the hardening of the stem usually comes with age, so this is likely to be the biggest it gets; or it just grows very slowly. Oh, and the "skin" of the cactus feels remarkably similar to the plastic which folding tables are made out of.

Any ideas or references are quite appreciated, and I understand if nobody can identify it, as the description probably narrows it down to only one or two species. I will post a picture as soon as I figure out how.