The cylindricas you have already got are probably S. cylindrica v patula which has long leaves that tend to arch outwards rather than stand upright. There is S. cylindrica v cylindrica which stands erect but it is not so common in the trade. My guess (without seeing a picture - hint, hint) is that you may have S. stuckyi which is almost cylindrical but has a slight channel running along the length of the leaf. Its the only other cylindrical leaf Sans I can think of at the moment which attains such a height. Others such as S. schweinfurthii & S. canaliculata are quite cylindrical but do not grow as big.

Hope this is of some help. Anyone else?

Thank you for you response. I think I'll go back and ask if I can take a pic of the Sans in question, and post it here.
Does this channel run throughout the whole leaf or just some part? And is it outwards or inwards?
Many thanks.

I went back and inspected the plant and it doesnt have a channel. Theres a "line" (for lack of better terminology)though, a very very tiny depression that runs through the whole leaf. The owner said it might be a stuckyi, but I'm wondering if this line or whatever is not the channel youre talking about. I chekced my cylindrica patula, and it doesnt seem to have this thing at the same place.
I tried looking for pics of the cylin. var cylin. but cant come up with any pics. The stuckyi pic I've found can be viewed with the link.
Oh , almost forgot what might be the most helpful : he said juvenile leaves are pretty flat. Does that help?

Here is a link that might be useful: S stuckyi

You can count the number of leaves per growth to help identify the plant. MAture S. stuckyi has 6 leaves, S. cylindrica has half that number.

Joe 'I just read that somewhere' DeRosa

Thanks Joe! yeah this one has more than 3 leaves to it, so guess its another vote for stuckyi.
BUT : I just read on another thread that the S cyl. cyl. has those flat juvenile leaves... the owner described the leaves as being flat at their juvenile stage...
Is this getting confusing?

According to N E Brown in his Sansevieria monograph, S. stuckyi when mature has just one (sometimes 2) leaves per growth. Certainly ties in with the mature S. stuckyi I have seen both pictured & in collections. I'll try to find some pictures to post.

Don't worry about the flat juvenile leaves, a lot of the cylindrical types have them.

Regarding the channel, it is as you say, just a depression rather than a deep thing. If your plant is well watered & plump then the channell is barely noticable. When on the dry side it becomes more pronounced.

I'll try get some pics.

Thanks birdsnestsoup.
I'm looking forward to seeing the pics :)