Who knows where the dividing line for Rebutia is? It's apparently polphyletic according to some multigene phylogenies done about a decade ago. All sorts of stuff mixed in there... Here's a tree and a 2007 paper from amjbot below. http://m.amjbot.org/content/98/1/44/F4.large.jpg -Ming Here is a link that might be useful: phylogenetic placement of rebutia etc.

Gymnocalycium mihanovichii.

cactusj: ".. but the Gymnocalycium isn't yellow because it's overwatered, it's a variagated specimen." Oh, ok. I thought it might be variegation but my Gymno turned a bit yellow once so I thought yours might've too. You said it is squishy. That makes me think it might be rot but it doesn't look like rot in the picture. The roots look healthy. You said the wrinkly area is covered by dirt. I'd plant it at a depth where the roots and green part meet so the bottom of the green part is resting on the potting mix and the roots are covered. I'd raise the wrinkly lower part out of the soil and keep an eye on it. I haven't grown plants in a hotter climate. If I moved to Los Angeles tomorrow and had to pick a window with full sun or full shade for plants I'd pick the one with full sun. If the window becomes too toasty you can put something like an insect screen in the window to block out some of the light and heat. I think my Gymno was plump only a short time during the Spring. Then the heat came. I kept watering it but didn't worry that is was wrinkling. Your G. horstii might not like as much sun as mine but I wouldn't put it in a full shade window. cactusj: "Everytime I would bring it onto the full shade porch it would improve a day later, it made me think the Gymno was suffering from the heat." That makes sense to me. I haven't tried that with my wrinkly cacti. Generally they might prefer cooler summer temperatures compared to a lot of other desert cacti. Just now I did some Googling and found www.cactus-art.biz says this cactus is a summer grower and likes more water than the average desert cactus. My experience has been, generally, the greener cacti like more water. The web page also suggests light shade. An insect screen would provide that.

The Aloe is likely a hybrid. The Euph. looks to possibly be a monstrose form of some sp.. 6. I think is a Gymnocalycium sp. 7. Looks like an Aeonium in form. Some sedums have this form, but are usually not this large. 8. You may be able to I.D. this Mammillaria at the CactiGuide site. Look for Mamms that bifurcate vs. ones that stay single. It looks like a common one so you should be able to find it. Sorry I don't have any complete I.D.'s but maybe the leads will help.