Suzyanne,
It is normal for Mammillaria pilcayensis (note spelling), to lean over when it gets large. Your plants must be very fine specimens at 1' tall. Use a google image search on the (correct) name and you will see many examples of this species.

Good growing

suze - i suggest you post this q at TGF. cactusjordi, cactuspolecat and other extremely knowledgable cactophiles will certain be able to help you understand what is happening and how to correct it....(and no popups!)

Here is a link that might be useful: TGF C&S

Suzyanne,
What is happening is that with extreme age these columnar varieties often tend to lean over and sprout offsets from the base and sides. Here is an example

http://www.brunero.it/cactus/mammillaria_pilcayensis.jpg

If you think it needs "correcting" for cosmetic reasons you could behead the plants and root the tops down. The stumps will eventually produce offsets for you. You will have to ensure that the wounds are healed over by letting the cut surfaces dry for a few days.
This species is deemed by some authorities to be a subspecies of Mammillaria spinosissima. The website http://www.mammillarias.net/ has a great gallery of photos of Mammillarias including some of M. pilcayensis (as M. spinosissima ssp pilcayensis).

cochemiea -
in re-reading my earlier post, i realized it did not read as i intended. i did not mean that suzyanne should post there INSTEAD of here, rather in addition to. i name-dropped thinking she might recognize these posters, not that there were no knowledgeable cactophiles here. i didnt offer suggestions on her q because i am not knowledgeable on cactus; my interest is in succulents. however, the no-popup advantage holds.

revised post:

suze -
you may also want to post this q at tgf. see link below.

Yes, I see your point. I have a pop-up blocker so I don't get the aggravation of them and tend not to appreciate the annoyance they would give to others.
TGF is a good forum, I have not posted there but the few times I have read their material it has been very interesting and factually sound.
Just had another look this morning and they have some great photos, worth browsing whether you post a q or not.

Regards

Cochemiea

Hi. Thanks for the information. I looked at the cactus picture, and it leans a little like mine, but looks brownish at the bottom, and mine is all green. Mine does, however, have a baby at the bottom of one of the two.

I tried the link listed, and I can go there, but cannot post a question. There is a note at the bottom of the page that says I cannot post a new question there. Perhaps I just don't know how to use it.

Anyway, I guess my cacti are OK. I don't want to cut them off, so I'll just see how they do. Thanks!

Suzyanne