Some form of Cleisto cactus, perhaps C. strausii, somewhat etoliated..
Bill in SC

I reckon Cleistocactus straussii too!

CP

Pointy heads! They might need more light, or they might need more water and fertiliser during the growing season. This one grows vigorously during the summer with plentiful water, takes all the sun I can offer (possibly a touch of shade in Oklahoma, probably not), but it also extremely cold hardy and tolerant of water in winter. Treating them hard will produce slow narrow growth. Growing them in dim light produces very tall narrow growth.

Hmmm.. S_B: Most things I've read about it say they are very rot prone, indicating to me that it would not like winter water. Mine did get plenty of water this summer with no adverse affects... Interesting comments from your above post...
Bill in SC

Well, they didn't get their pointy heads from me. I just bought these 2 weeks ago. I now have them in the greenhouse so they should be getting plenty of light. I looked them up on Desert Tropicals and it does say to water generously in the summer.
Thanks for all your comments.

WindsurfGirl

I've read the rot-prone description, their high-Andes location and thick spination marks them out as being rot-prone, but they really are very trouble-free here. This is one of the few cacti that I leave outside completely unprotected right through the summer. They have been overwintered outside in some sheltered locations in England.

Wowzer. I too have had relative ease growing a yellow spined variety of Cleisto. I had the growing season reversed for many years and watered in the Winter maybe once a month or every other month if I forgot. It barely grew during this time. Moved it out on the balcony a few years ago and it looks so much happier and it grew a lot. Summer rains soak it good but high temp's and direct Summer sun keep it healthy. Winter time it gets a drink once a month (indoors) or so till Decemberish then I'll cut 'em off for a month or two depending on the number of sunny days we may or may not get till Marchish. My gas heat can really dry 'em out quick when the furnace runs a lot.